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A crystal or crystalline solid is a
solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The molecules in a solid are closely packed together and contain the least amount of kinetic energy. A solid is characterized by structural ...

solid
material whose constituents (such as
atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of ato ...

atom
s,
molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral group of two or more atoms held together by chemical bo ...

molecule
s, or
ion An ion () is a particle In the Outline of physical science, physical sciences, a particle (or corpuscule in older texts) is a small wikt:local, localized physical body, object to which can be ascribed several physical property, physical or ...
s) are arranged in a highly ordered microscopic structure, forming a
crystal lattice A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macrosco ...
that extends in all directions. In addition, macroscopic
single crystal A single-crystal, or monocrystalline, solid is a material in which the crystal lattice of the entire sample is continuous and unbroken to the edges of the sample, with no grain boundaries.RIWD. "Reade Advanced Materials - Single Crystals". ''ww ...
s are usually identifiable by their geometrical shape, consisting of flat
faces The face is the front of an animal's head that features three of the head's Sense, sense organs, the eyes, nose, and mouth, and through which animals express many of their Emotion, emotions. The face is crucial for human Personal identity, ident ...
with specific, characteristic orientations. The scientific study of crystals and crystal formation is known as
crystallography Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids (see crystal structure). The word "crystallography" is derived from the Greek words ''crystallon'' "cold drop, frozen drop", with its mean ...
. The process of crystal formation via mechanisms of
crystal growth A crystal is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. Crystal growth is a major stage of a crystallization, crystallization process, and co ...
is called
crystallization Crystallization or crystallisation is the process by which a solid forms, where the atoms or molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five car ...

crystallization
or
solidification Freezing is a phase transition In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure, properties, ...
. The word ''crystal'' derives from the
Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages () ...
word (), meaning both "
ice Ice is water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere an ...

ice
" and "
rock crystal Quartz is a hard, crystalline mineral composed of silicon and oxygen atoms. The atoms are linked in a continuous framework of SiO4 silicon-oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tetrahedra, g ...
", from (), "icy cold, frost". Examples of large crystals include
snowflake A snowflake is a single ice crystal that has achieved a sufficient size, and may have amalgamated with others, then falls through the Earth's atmosphere as snow.Knight, C.; Knight, N. (1973). Snow crystals. A snowflake is also the name of a pers ...

snowflake
s,
diamond Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic The diamond cubic crystal structure is a repeating pattern of 8 atoms that certain materials may adopt as they solidify. Wh ...

diamond
s, and
table salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its natural form as a crystallinity, crystalline mineral is known as rock salt or halite. Sa ...
. Most inorganic solids are not crystals but
polycrystal A crystallite is a small or even microscopic crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice ...
s, i.e. many microscopic crystals fused together into a single solid. Examples of polycrystals include most
metals A metal (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 mi ...
, rocks,
ceramics A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant Corrosion is a Erosion, natural process that converts a refined metal into a more chemically stable form such as oxide, hydroxide, carbonate or sulfide. It ...
, and
ice Ice is water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere an ...

ice
. A third category of solids is
amorphous solid In condensed matter physics and materials science The interdisciplinary field of materials science, also commonly termed materials science and engineering, covers the design and discovery of new materials, particularly solids. The intellec ...
s, where the atoms have no periodic structure whatsoever. Examples of amorphous solids include
glass Glass is a non- crystalline, often transparency and translucency, transparent amorphous solid, that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by ...

glass
,
wax , a typical wax ester. Image:Beeswax foundation.jpg, Commercial honeycomb foundation, made by pressing beeswax between patterned metal rollers. Waxes are a diverse class of organic compounds that are lipophilic, malleability, malleable solids ne ...
, and many
plastic Plastics are a wide range of synthetic polymers, synthetic or semi-synthetic materials that use polymers as a main ingredient. Their Plasticity (physics), plasticity makes it possible for plastics to be Injection moulding, moulded, Extrusion, extr ...

plastic
s. Despite the name, lead crystal, crystal glass, and related products are ''not'' crystals, but rather types of glass, i.e. amorphous solids. Crystals are often used in
pseudoscientific Pseudoscience consists of statements, belief A belief is an Attitude (psychology), attitude that something is the case, or that some proposition about the world is truth, true. In epistemology, philosophers use the term "belief" to refer to ...
practices such as crystal therapy, and, along with
gemstone A gemstone (also called a gem, fine gem, jewel, precious stone, or semi-precious stone) is a piece of mineral crystal which, in cut and polished form, is used to make jewellery, jewelry or other adornments. However, certain Rock (geology), rocks ...

gemstone
s, are sometimes associated with spellwork in
Wicca Wicca (), also termed Pagan Witchcraft, is a modern Pagan religion. Scholars of religion categorise it as both a new religious movement and as part of the occultist stream of Western esotericism. It was developed in England England is ...
n beliefs and related religious movements.


Crystal structure (microscopic)

The scientific definition of a "crystal" is based on the microscopic arrangement of atoms inside it, called the
crystal structure In crystallography Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids (see crystal structure). The word "crystallography" is derived from the Greek words ''crystallon'' "cold drop, frozen ...
. A crystal is a solid where the atoms form a periodic arrangement. (
Quasicrystal A quasiperiodic crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all dire ...

Quasicrystal
s are an exception, see
below Below may refer to: *Earth *Ground (disambiguation) *Soil *Floor *Bottom (disambiguation) *Less than *Temperatures below freezing *Hell or underworld People with the surname *Fred Below (1926–1988), American blues drummer *Fritz von Below (1853 ...
). Not all solids are crystals. For example, when liquid water starts freezing, the phase change begins with small ice crystals that grow until they fuse, forming a ''
polycrystalline A crystallite is a small or even microscopic crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice ...
'' structure. In the final block of ice, each of the small crystals (called "
crystallite A crystallite is a small or even microscopic crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice ...
s" or "grains") is a true crystal with a periodic arrangement of atoms, but the whole polycrystal does ''not'' have a periodic arrangement of atoms, because the periodic pattern is broken at the
grain boundaries of a polycrystalline A crystallite is a small or even microscopic crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, for ...
. Most macroscopic
inorganic In chemistry Chemistry is the scientific discipline involved with Chemical element, elements and chemical compound, compounds composed of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they under ...
solids are polycrystalline, including almost all
metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts Electrical resistivity and conductivity, el ...

metal
s,
ceramic A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing a nonmetallic mineral, such as clay, at a high temperature. Common examples are earthenware, porcelain, and brick. ...
s,
ice Ice is water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere an ...

ice
,
rocks A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its Chemical compound, chemical composition and the way in which it is formed. Rocks form the Earth's oute ...
, etc. Solids that are neither crystalline nor polycrystalline, such as
glass Glass is a non- crystalline, often transparency and translucency, transparent amorphous solid, that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by ...

glass
, are called ''
amorphous solid In condensed matter physics and materials science The interdisciplinary field of materials science, also commonly termed materials science and engineering, covers the design and discovery of new materials, particularly solids. The intellec ...
s'', also called
glass Glass is a non- crystalline, often transparency and translucency, transparent amorphous solid, that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by ...

glass
y, vitreous, or noncrystalline. These have no periodic order, even microscopically. There are distinct differences between crystalline solids and amorphous solids: most notably, the process of forming a glass does not release the latent heat of fusion, but forming a crystal does. A crystal structure (an arrangement of atoms in a crystal) is characterized by its ''unit cell'', a small imaginary box containing one or more atoms in a specific spatial arrangement. The unit cells are
stacked ''Stacked'' is an American television Situation comedy, sitcom that aired on Fox Broadcasting Company, Fox from April 13, 2005 to January 11, 2006. Premise ''Stacked'' was described as the opposite of ''Cheers'', instead of a smart person in a " ...
in three-dimensional space to form the crystal. The symmetry of a crystal is constrained by the requirement that the unit cells stack perfectly with no gaps. There are 219 possible crystal symmetries, called crystallographic space groups. These are grouped into 7
crystal system In crystallography Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids (see crystal structure). The word "crystallography" is derived from the Greek words ''crystallon'' "cold drop, frozen ...
s, such as
cubic crystal system 200px, A network model of a primitive cubic system In crystallography, the cubic (or isometric) crystal system is a crystal system where the Crystal_structure#Unit_cell, unit cell is in the shape of a cube. This is one of the most common and simpl ...
(where the crystals may form cubes or rectangular boxes, such as
halite Halite ( or ), commonly known as rock salt, is a type of salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its natural form as a cry ...
shown at right) or
hexagonal crystal system In crystallography, the hexagonal crystal family is one of the six crystal families, which includes two crystal systems (hexagonal and trigonal) and two lattice systems (hexagonal and rhombohedral). While commonly confused, the trigonal crystal s ...
(where the crystals may form hexagons, such as ordinary water ice).


Crystal faces and shapes

Crystals are commonly recognized by their shape, consisting of flat faces with sharp angles. These shape characteristics are not ''necessary'' for a crystal—a crystal is scientifically defined by its microscopic atomic arrangement, not its macroscopic shape—but the characteristic macroscopic shape is often present and easy to see.
Euhedral Euhedral pyrite crystals Euhedral crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that ext ...
crystals are those with obvious, well-formed flat faces. Anhedral crystals do not, usually because the crystal is one grain in a polycrystalline solid. The flat faces (also called
facet Facets () are flat faces on geometric shapes. The organization of naturally occurring facets was key to early developments in crystallography Crystallography is the experimental science of determining the arrangement of atoms in crystalline so ...
s) of a
euhedral Euhedral pyrite crystals Euhedral crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that ext ...
crystal are oriented in a specific way relative to the underlying atomic arrangement of the crystal: they are planes of relatively low
Miller index Miller indices form a notation system in crystallography for planes in Bravais lattice, crystal (Bravais) lattices. In particular, a family of lattice planes is determined by three integers ''h'', ''k'', and ''ℓ'', the ''Miller indices''. ...
. This occurs because some surface orientations are more stable than others (lower
surface energy Surface free energy or interfacial free energy or surface energy quantifies the disruption of intermolecular bonds that occurs when a surface is created. In the physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epist ...
). As a crystal grows, new atoms attach easily to the rougher and less stable parts of the surface, but less easily to the flat, stable surfaces. Therefore, the flat surfaces tend to grow larger and smoother, until the whole crystal surface consists of these plane surfaces. (See diagram on right.) One of the oldest techniques in the science of
crystallography Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids (see crystal structure). The word "crystallography" is derived from the Greek words ''crystallon'' "cold drop, frozen drop", with its mean ...
consists of measuring the three-dimensional orientations of the faces of a crystal, and using them to infer the underlying
crystal symmetry In crystallography Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids (see crystal structure). The word "crystallography" is derived from the Greek words ''crystallon'' "cold drop, frozen ...
. A crystal's habit is its visible external shape. This is determined by the
crystal structure In crystallography Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids (see crystal structure). The word "crystallography" is derived from the Greek words ''crystallon'' "cold drop, frozen ...
(which restricts the possible facet orientations), the specific crystal chemistry and bonding (which may favor some facet types over others), and the conditions under which the crystal formed.


Occurrence in nature


Rocks

By volume and weight, the largest concentrations of crystals in the Earth are part of its solid
bedrock Bedrock in geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of which it is composed, and ...
. Crystals found in rocks typically range in size from a fraction of a millimetre to several centimetres across, although exceptionally large crystals are occasionally found. , the world's largest known naturally occurring crystal is a crystal of
beryl Beryl ( ) is a mineral composed of beryllium Beryllium is a chemical element with the Symbol (chemistry), symbol Be and atomic number 4. It is a Abundance of the chemical elements#Universe, relatively rare element in the universe, usually ...
from Malakialina,
Madagascar Madagascar (; mg, Madagasikara), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), and previously known as the Malagasy Republic, is an island country in the Indian Ocean, a ...

Madagascar
, long and in diameter, and weighing . Some crystals have formed by
magmatic 300px, Hawaii Hawaii ( ; haw, Hawaii or ) is a U.S. state in the Western United States, in the Pacific Ocean about 2,000 miles (3,200 km) from the U.S. mainland. It is the only state outside North America, the only island state, and ...
and metamorphic processes, giving origin to large masses of crystalline
rock Rock most often refers to: * Rock (geology) A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its Chemical compound, chemical composition and the way in w ...
. The vast majority of
igneous rocks Igneous rock (derived from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the p ...

igneous rocks
are formed from molten magma and the degree of crystallization depends primarily on the conditions under which they solidified. Such rocks as
granite Granite () is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools ...

granite
, which have cooled very slowly and under great pressures, have completely crystallized; but many kinds of
lava of pāhoehoe lava, Hawaii, United States , Iceland in 1984 Lava is molten Rock (geology), rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon. Magma is generated by the inte ...

lava
were poured out at the surface and cooled very rapidly, and in this latter group a small amount of amorphous or
glass Glass is a non- crystalline, often transparency and translucency, transparent amorphous solid, that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by ...

glass
y matter is common. Other crystalline rocks, the metamorphic rocks such as
marble Marble is a metamorphic rock composed of recrystallized carbonate minerals, most commonly calcite or Dolomite (mineral), dolomite. Marble is typically not Foliation (geology), foliated, although there are exceptions. In geology, the term ''marb ...

marble
s, mica-schists and
quartzite Quartzite is a hard, non- foliated metamorphic rock which was originally pure quartz Quartz is a hard, crystalline mineral composed of silicon and oxygen atoms. The atoms are linked in a continuous framework of SiO4 silicon-oxygen Tetrahed ...

quartzite
s, are recrystallized. This means that they were at first fragmental rocks like
limestone Limestone is a common type of carbonate rock, carbonate sedimentary rock. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science), crystal forms of calcium carbonate (). Limestone forms ...

limestone
,
shale Shale is a fine-grained, clastic sedimentary rock Sedimentary rocks are types of Rock (geology), rock that are formed by the accumulation or deposition of mineral or organic matter, organic particles at the Earth's surface, followed by Cementa ...

shale
and
sandstone Sandstone is a clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains. Sandstones make up about 20 to 25 percent of all sedimentary rocks. Most sandstone is composed of quartz o ...

sandstone
and have never been in a
molten Melting, or fusion, is a physical process that results in the phase transition of a chemical substance, substance from a solid to a liquid. This occurs when the internal energy of the solid increases, typically by the application of heat or pr ...
condition nor entirely in solution, but the high temperature and pressure conditions of
metamorphism upright=1.35, Schematic representation of a metamorphic reaction. Abbreviations of minerals: act = actinolite; chl = Chlorite group">chlorite; ep = epidote; gt = garnet; hbl = hornblende; plag = plagioclase. Two minerals represented in the figure ...
have acted on them by erasing their original structures and inducing recrystallization in the solid state. Other rock crystals have formed out of precipitation from fluids, commonly water, to form druses or
quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tetrahedra, ...

quartz
veins.
Evaporite evaporated from the Dead Sea, Israel Evaporite () is the term for a water-soluble mineral sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently sediment transport, ...
s such as
halite Halite ( or ), commonly known as rock salt, is a type of salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its natural form as a cry ...
,
gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard/ sidewalk chalk, and drywal ...

gypsum
and some limestones have been deposited from aqueous solution, mostly owing to
evaporation File:10. Ладење при испарување.ogv, 280px, Demonstration of evaporative cooling. When the sensor is dipped in ethanol and then taken out to evaporate, the instrument shows progressively lower temperature as the ethanol evapor ...

evaporation
in arid climates.


Ice

Water-based
ice Ice is water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere an ...

ice
in the form of
snow Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water throughout i ...

snow
,
sea ice Sea ice arises as seawater freezes. Because ice is less dense than water, it floats on the ocean's surface (as does fresh water ice, which has an even lower density). Sea ice covers about 7% of the Earth's surface and about 12% of the world's ...

sea ice
, and
glacier A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its Ablation#Glaciology, ablation over many years, often Century, centuries. Glaciers slowl ...

glacier
s are common crystalline/polycrystalline structures on Earth and other planets. A single
snowflake A snowflake is a single ice crystal that has achieved a sufficient size, and may have amalgamated with others, then falls through the Earth's atmosphere as snow.Knight, C.; Knight, N. (1973). Snow crystals. A snowflake is also the name of a pers ...

snowflake
is a single crystal or a collection of crystals, while an
ice cube O'Shea Jackson (born June 15, 1969), better known by his stage name Ice Cube, is an American rapper, actor, and filmmaker. His lyrics on N.W.A's 1988 album ''Straight Outta Compton'' contributed to gangsta rap's widespread popularity,Steve Huey ...

ice cube
is a
polycrystal A crystallite is a small or even microscopic crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice ...
.


Organigenic crystals

Many living
organisms In biology, an organism () is any organic, life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy (biology), taxonomy into groups such as Multice ...

organisms
are able to produce crystals, for example
calcite Image:Calcite.png, 235px, Crystal structure of calcite Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). The Mohs scale of mineral hardness, based on Scr ...

calcite
and
aragonite Aragonite is a carbonate mineral, one of the three most common naturally occurring polymorphism (materials science), crystal forms of calcium carbonate, (the other forms being the minerals calcite and vaterite). It is formed by biological and phy ...

aragonite
in the case of most
mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda. The members are known as molluscs or mollusks (). Around 85,000 extant taxon, extant species of molluscs are recognized. The number of fossil species is es ...
s or
hydroxylapatite Hydroxyapatite, also called hydroxylapatite (HA), is a naturally occurring mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned ...
in the case of
vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic ma ...
s.


Polymorphism and allotropy

The same group of atoms can often solidify in many different ways. Polymorphism is the ability of a solid to exist in more than one crystal form. For example, water
ice Ice is water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere an ...

ice
is ordinarily found in the hexagonal form Ice Ih, but can also exist as the cubic Ice Ic, the
rhombohedral In geometry Geometry (from the grc, γεωμετρία; ''wikt:γῆ, geo-'' "earth", ''wikt:μέτρον, -metron'' "measurement") is, with arithmetic, one of the oldest branches of mathematics. It is concerned with properties of space th ...

rhombohedral
ice II Ice II is a rhombohedral In geometry Geometry (from the grc, γεωμετρία; ''wikt:γῆ, geo-'' "earth", ''wikt:μέτρον, -metron'' "measurement") is, with arithmetic, one of the oldest branches of mathematics. It is concerned w ...
, and many other forms. The different polymorphs are usually called different '' phases''. In addition, the same atoms may be able to form noncrystalline phases. For example, water can also form
amorphous ice Amorphous ice (non-crystalline or "vitreous" ice) is an amorphous solid In condensed matter physics and materials science The interdisciplinary field of materials science, also commonly termed materials science and engineering, covers the d ...
, while SiO2 can form both
fused silica Fused quartz or fused silica is glass Glass is a non- crystalline, often transparency and translucency, transparent amorphous solid, that has widespread practical, technological, and decorative use in, for example, window panes, tableware, a ...
(an amorphous glass) and
quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tetrahedra, ...

quartz
(a crystal). Likewise, if a substance can form crystals, it can also form polycrystals. For pure chemical elements, polymorphism is known as
allotropy Allotropy or allotropism () is the property of some chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting o ...
. For example,
diamond Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic The diamond cubic crystal structure is a repeating pattern of 8 atoms that certain materials may adopt as they solidify. Wh ...

diamond
and
graphite Graphite (), archaically referred to as plumbago, is a crystalline form of the element carbon Carbon (from la, carbo "coal") is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table ...

graphite
are two crystalline forms of
carbon Carbon (from la, carbo "coal") is a chemical element with the Symbol (chemistry), symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—making four electrons available to form covalent bond, covalent chemical bonds. ...
, while
amorphous carbonAmorphous carbon is free, reactive carbon that does not have any crystalline A crystal or crystalline solid is a solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The molecules ...
is a noncrystalline form. Polymorphs, despite having the same atoms, may have wildly different properties. For example, diamond is among the hardest substances known, while graphite is so soft that it is used as a lubricant. Polyamorphism is a similar phenomenon where the same atoms can exist in more than one
amorphous solid In condensed matter physics and materials science The interdisciplinary field of materials science, also commonly termed materials science and engineering, covers the design and discovery of new materials, particularly solids. The intellec ...
form.


Crystallization

Crystallization is the process of forming a crystalline structure from a fluid or from materials dissolved in a fluid. (More rarely, crystals may be deposited directly from gas; see
thin-film deposition A thin film is a layer of material ranging from fractions of a nanometer (monolayer) to several micrometre, micrometers in thickness. The controlled synthesis of materials as thin films (a process referred to as deposition) is a fundamental step i ...
and
epitaxy Epitaxy refers to a type of crystal growth or material deposition in which new crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic ...
.) Crystallization is a complex and extensively-studied field, because depending on the conditions, a single fluid can solidify into many different possible forms. It can form a
single crystal A single-crystal, or monocrystalline, solid is a material in which the crystal lattice of the entire sample is continuous and unbroken to the edges of the sample, with no grain boundaries.RIWD. "Reade Advanced Materials - Single Crystals". ''ww ...
, perhaps with various possible phases,
stoichiometries Stoichiometry is the calculation of reactants and Product (chemistry), products in chemical reactions in chemistry. Stoichiometry is founded on the law of conservation of mass where the total mass of the reactants equals the total mass of the ...
, impurities,
defects A defect is a physical, functional, or aesthetic attribute of a product or service that exhibits that the product or service failed to meet one of the desired specifications. Defect, defects or defected may also refer to: Examples * Angular defect ...
, and
habits A habit (or wont as a humorous and formal term) is a routine of behavior that is repeated regularly and tends to occur Subconscious, subconsciously.
. Or, it can form a
polycrystal A crystallite is a small or even microscopic crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice ...
, with various possibilities for the size, arrangement, orientation, and phase of its grains. The final form of the solid is determined by the conditions under which the fluid is being solidified, such as the chemistry of the fluid, the
ambient pressure Ambient or Ambiance or Ambience may refer to: Music and sound * Ambience (sound recording), also known as atmospheres or backgrounds * Ambient music, a genre of music that puts an emphasis on tone and atmosphere * ''Ambient'' (album), by Moby * ...
, the
temperature Temperature is a physical quantity that expresses hot and cold. It is the manifestation of thermal energy, present in all matter, which is the source of the occurrence of heat, a flow of energy, when a body is in contact with another that is ...

temperature
, and the speed with which all these parameters are changing. Specific industrial techniques to produce large single crystals (called ''
boules ''Boules'' () is a collective name for a wide range of games similar to bowls and bocce (In French: jeu or jeux, in Italian: gioco or giochi) in which the objective is to throw or roll heavy balls (called in France, and in Italy) as close as poss ...
'') include the
Czochralski process The Czochralski method, also Czochralski technique or Czochralski process, is a method of crystal growth A crystal is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three ...

Czochralski process
and the
Bridgman techniqueBridgman is a surname, and may refer to: * David Bridgman, Australian architect * Elijah Coleman Bridgman (1801–1861), American missionary in China * Frederick Arthur Bridgman (1847-1928), American artist * George Bridgman (1865-1943), anatomis ...
. Other less exotic methods of crystallization may be used, depending on the physical properties of the substance, including
hydrothermal synthesis crystal grown by the hydrothermal method Hydrothermal synthesis includes the various techniques of crystallizing substances from high-temperature aqueous solution An aqueous solution is a solution Image:SaltInWaterSolutionLiquid.jpg, Making ...
, sublimation, or simply solvent-based crystallization. Large single crystals can be created by geological processes. For example,
selenite Selenite may refer to: Substances containing selenium *A selenium-containing anion or ionic compound with the SeO32− anion: **Selenite (ion), anion is a selenium oxoanion with the chemical formula SeO32− ***Selenous acid, the conjugate acid, wi ...
crystals in excess of 10
meter The metre ( Commonwealth spelling) or meter ( American spelling; see spelling differences) (from the French unit , from the Greek noun , "measure", and cognate with Sanskrit Sanskrit (, attributively , ''saṃskṛta-'', nominalization, no ...

meter
s are found in the
Cave of the Crystals Cave of the Crystals or Giant Crystal Cave () is a cave A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering Weathering is the breaking down of rocks ...
in Naica, Mexico. For more details on geological crystal formation, see above. Crystals can also be formed by biological processes, see above. Conversely, some organisms have special techniques to ''prevent'' crystallization from occurring, such as
antifreeze protein Antifreeze proteins (AFPs) or ice structuring proteins (ISPs) refer to a class of polypeptides produced by certain animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological ...
s.


Defects, impurities, and twinning

An ''ideal'' crystal has every atom in a perfect, exactly repeating pattern. However, in reality, most crystalline materials have a variety of
crystallographic defect Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids (see crystal structure). The word "crystallography" is derived from the Greek words ''crystallon'' "cold drop, frozen drop", with its mean ...
s, places where the crystal's pattern is interrupted. The types and structures of these defects may have a profound effect on the properties of the materials. A few examples of crystallographic defects include
vacancy defect In crystallography Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids (see crystal structure). The word "crystallography" is derived from the Greek words ''crystallon'' "cold drop, frozen ...
s (an empty space where an atom should fit),
interstitial defect An interstitial defect is a type of point crystallographic defect where an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by havin ...
s (an extra atom squeezed in where it does not fit), and
dislocation In materials science The interdisciplinary field of materials science, also commonly termed materials science and engineering, covers the design and discovery of new materials, particularly solids. The intellectual origins of materials scienc ...
s (see figure at right). Dislocations are especially important in
materials science The Interdisciplinarity, interdisciplinary field of materials science, also commonly termed materials science and engineering, covers the design and discovery of new materials, particularly solids. The intellectual origins of materials science ste ...
, because they help determine the mechanical strength of materials. Another common type of crystallographic defect is an
impurity Impurities are chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ...
, meaning that the "wrong" type of atom is present in a crystal. For example, a perfect crystal of
diamond Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic The diamond cubic crystal structure is a repeating pattern of 8 atoms that certain materials may adopt as they solidify. Wh ...

diamond
would only contain
carbon Carbon (from la, carbo "coal") is a chemical element with the Symbol (chemistry), symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—making four electrons available to form covalent bond, covalent chemical bonds. ...
atoms, but a real crystal might perhaps contain a few
boron Boron is a chemical element with the Chemical symbol, symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the ''boron g ...
atoms as well. These boron impurities change the diamond's color to slightly blue. Likewise, the only difference between
ruby A ruby is a pink to blood-red coloured gemstone A gemstone (also called a gem, fine gem, jewel, precious stone, or semi-precious stone) is a piece of mineral crystal which, in cut and polished form, is used to make jewellery, jewelry or othe ...

ruby
and
sapphire Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide () with trace amounts of elements such as iron, titanium, chromium, vanadium, or magnesium. The name sapphire is derived from the Latin "saphir ...

sapphire
is the type of impurities present in a
corundum Corundum is a crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all direction ...

corundum
crystal. In
semiconductor A semiconductor material has an electrical conductivity Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that quantifies how strongly it resists electric curre ...
s, a special type of impurity, called a
dopant A dopant, also called a doping agent, is a trace of impurity element that is introduced into a chemical material to alter its original electrical or optics, optical properties. The amount of dopant necessary to cause changes is typically very low ...
, drastically changes the crystal's electrical properties.
Semiconductor device A semiconductor device is an electronic component that relies on the electronics, electronic properties of a semiconductor material (primarily silicon, germanium, and gallium arsenide, as well as organic semiconductors) for its function. Semicon ...
s, such as
transistor file:MOSFET Structure.png, upright=1.4, Metal-oxide-semiconductor field-effect transistor (MOSFET), showing Metal gate, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A ...

transistor
s, are made possible largely by putting different semiconductor dopants into different places, in specific patterns.
Twinning Twinning (making a twin of) may refer to: * In biology and agriculture, producing two offspring (i.e., twins) at a time, or having a tendency to do so; * Twin towns and sister cities, towns and cities involved in town twinning * Twinning institut ...
is a phenomenon somewhere between a crystallographic defect and a
grain boundary of a polycrystalline A crystallite is a small or even microscopic crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, for ...
. Like a grain boundary, a twin boundary has different crystal orientations on its two sides. But unlike a grain boundary, the orientations are not random, but related in a specific, mirror-image way.
Mosaicity In crystallography Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids (see crystal structure). The word "crystallography" is derived from the Greek words ''crystallon'' "cold drop, frozen d ...
is a spread of crystal plane orientations. A mosaic crystal consists of smaller crystalline units that are somewhat misaligned with respect to each other.


Chemical bonds

In general, solids can be held together by various types of
chemical bond A chemical bond is a lasting attraction between atoms, ions or molecules that enables the formation of chemical compounds. The bond may result from the Coulomb's law, electrostatic force of attraction between oppositely charged ions as in ionic ...
s, such as
metallic bond Metallic bonding is a type of chemical bond A chemical bond is a lasting attraction between atoms, ions or molecules that enables the formation of chemical compounds. The bond may result from the Coulomb's law, electrostatic force of att ...
s,
ionic bond Ionic bonding is a type of chemical bonding that involves the electrostatic attraction between oppositely charged ions, or between two atoms with sharply different electronegativities, and is the primary interaction occurring in ionic compound ...
s,
covalent bond A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs, and the stable balance of attractive and repulsive forces between atoms, when they sh ...
s, van der Waals bonds, and others. None of these are necessarily crystalline or non-crystalline. However, there are some general trends as follows.
Metal A metal (from Ancient Greek, Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts Electrical resistivity and conductivity, el ...

Metal
s are almost always polycrystalline, though there are exceptions like
amorphous metal An amorphous metal (also known as metallic glass or glassy metal) is a solid metallic material, usually an alloy, with disordered atomic-scale structure. Most metals are crystal A crystal or crystalline solid is a solid material whose co ...
and single-crystal metals. The latter are grown synthetically. (A microscopically-small piece of metal may naturally form into a single crystal, but larger pieces generally do not.)
Ionic compound structure of sodium chloride Sodium chloride , commonly known as salt (although sea salt also contains other chemical salt (chemistry), salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chlori ...
materials are usually crystalline or polycrystalline. In practice, large
salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its natural form as a crystallinity, crystalline mineral is known as rock salt or halite. Sa ...
crystals can be created by solidification of a
molten Melting, or fusion, is a physical process that results in the phase transition of a chemical substance, substance from a solid to a liquid. This occurs when the internal energy of the solid increases, typically by the application of heat or pr ...
fluid, or by crystallization out of a solution.
Covalently bonded A covalent bond is a chemical bond A chemical bond is a lasting attraction between atoms, ions or molecules that enables the formation of chemical compounds. The bond may result from the Coulomb's law, electrostatic force of attraction bet ...
solids (sometimes called covalent network solids) are also very common, notable examples being
diamond Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic The diamond cubic crystal structure is a repeating pattern of 8 atoms that certain materials may adopt as they solidify. Wh ...

diamond
and
quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tetrahedra, ...

quartz
. Weak
van der Waals force In molecular physics, the Van der Waals force, named after Dutch physicist Johannes Diderik van der Waals, is a distance-dependent interaction between atoms or molecules. Unlike ionic bond, ionic or covalent bonds, these attractions do not result ...
s also help hold together certain crystals, such as crystalline molecular solids, as well as the interlayer bonding in
graphite Graphite (), archaically referred to as plumbago, is a crystalline form of the element carbon Carbon (from la, carbo "coal") is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table ...

graphite
.
Polymer A polymer (; Greek ''wikt:poly-, poly-'', "many" + ''wikt:-mer, -mer'', "part") is a Chemical substance, substance or material consisting of very large molecules, or macromolecules, composed of many Repeat unit, repeating subunits. Due to their ...

Polymer
materials generally will form crystalline regions, but the lengths of the molecules usually prevent complete crystallization—and sometimes polymers are completely amorphous.


Quasicrystals

A
quasicrystal A quasiperiodic crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all dire ...

quasicrystal
consists of arrays of atoms that are ordered but not strictly periodic. They have many attributes in common with ordinary crystals, such as displaying a discrete pattern in
x-ray diffraction X-ray crystallography (XRC) is the experimental science determining the atomic and molecular structure of a crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a ...
, and the ability to form shapes with smooth, flat faces. Quasicrystals are most famous for their ability to show five-fold symmetry, which is impossible for an ordinary periodic crystal (see
crystallographic restriction theorem The crystallographic restriction theorem in its basic form was based on the observation that the rotational symmetries Rotational symmetry, also known as radial symmetry in biology, is the property a shape has when it looks the same after some ro ...
). The
International Union of Crystallography The International Union of Crystallography (IUCr) is an organisation devoted to the international promotion and coordination of the science of crystallography Crystallography is the experimental science of determining the arrangement of atoms in ...
has redefined the term "crystal" to include both ordinary periodic crystals and quasicrystals ("any solid having an essentially discrete
diffraction Diffraction refers to various phenomena that occur when a wave encounters an obstacle or opening. It is defined as the bending of waves around the corners of an obstacle or through an aperture In optics, an aperture is a hole or an openin ...
diagram"). Quasicrystals, first discovered in 1982, are quite rare in practice. Only about 100 solids are known to form quasicrystals, compared to about 400,000 periodic crystals known in 2004. The 2011
Nobel Prize in Chemistry ) , image = Nobel Prize.png , alt = A golden medallion with an embossed image of a bearded man facing left in profile. To the left of the man is the text "ALFR•" then "NOBEL", and on the right, the text (smaller) "NAT•" then "MD ...
was awarded to
Dan Shechtman Dan Shechtman ( he, דן שכטמן; born January 24, 1941)Dan Shechtman
. (PDF). Retriev ...

Dan Shechtman
for the discovery of quasicrystals.


Special properties from anisotropy

Crystals can have certain special electrical, optical, and mechanical properties that
glass Glass is a non- crystalline, often transparency and translucency, transparent amorphous solid, that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by ...

glass
and
polycrystal A crystallite is a small or even microscopic crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice ...
s normally cannot. These properties are related to the
anisotropy Anisotropy () is the property of a material which allows it to change or assume different properties in different directions as opposed to isotropy. It can be defined as a difference, when measured along different axes, in a material's physic ...
of the crystal, i.e. the lack of rotational symmetry in its atomic arrangement. One such property is the
piezoelectric effect Piezoelectricity (, ) is the electric charge that accumulates in certain solid materials—such as crystals, certain ceramics, and biological matter such as bone, DNA, and various proteins—in response to applied Stress (mechanics), mechanical st ...

piezoelectric effect
, where a voltage across the crystal can shrink or stretch it. Another is
birefringence Birefringence is the optical property of a material having a refractive index In optics, the refractive index (also known as refraction index or index of refraction) of a optical medium, material is a dimensionless number that describes how fas ...

birefringence
, where a double image appears when looking through a crystal. Moreover, various properties of a crystal, including
electrical conductivity Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that quantifies how strongly it resists electric current An electric current is a stream of charged particles, ...
, electrical permittivity, and
Young's modulus Young's modulus E, the Young modulus or the modulus of elasticity An elastic modulus (also known as modulus of elasticity) is a quantity that measures an object or substance's resistance to being deformed elastically (i.e., non-permanently) when ...
, may be different in different directions in a crystal. For example,
graphite Graphite (), archaically referred to as plumbago, is a crystalline form of the element carbon Carbon (from la, carbo "coal") is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table ...

graphite
crystals consist of a stack of sheets, and although each individual sheet is mechanically very strong, the sheets are rather loosely bound to each other. Therefore, the mechanical strength of the material is quite different depending on the direction of stress. Not all crystals have all of these properties. Conversely, these properties are not quite exclusive to crystals. They can appear in
glass Glass is a non- crystalline, often transparency and translucency, transparent amorphous solid, that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by ...

glass
es or
polycrystal A crystallite is a small or even microscopic crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice ...
s that have been made
anisotropic Anisotropy () is the property of a material which allows it to change or assume different properties in different directions as opposed to isotropy. It can be defined as a difference, when measured along different axes, in a material's physic ...
by Work hardening, working or stress (mechanics), stress—for example, photoelasticity, stress-induced birefringence.


Crystallography

''Crystallography'' is the science of measuring the
crystal structure In crystallography Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids (see crystal structure). The word "crystallography" is derived from the Greek words ''crystallon'' "cold drop, frozen ...
(in other words, the atomic arrangement) of a crystal. One widely used crystallography technique is X-ray diffraction. Large numbers of known crystal structures are stored in crystallographic databases.


Image gallery

File:Insulincrystals.jpg, Insulin crystals space manufacturing, grown in earth orbit. File:Hoar frost macro2.jpg, Hoar frost: A type of ice crystal (picture taken from a distance of about 5 cm). File:Gallium crystals.jpg, Gallium, a metal that easily forms large crystals. File:Apatite-Rhodochrosite-Fluorite-169799.jpg, An apatite crystal sits front and center on cherry-red rhodochroite rhombs, purple fluorite cubes, quartz and a dusting of brass-yellow pyrite cubes. File:Monokristalines Silizium für die Waferherstellung.jpg, Boule (crystal), Boules of silicon, like this one, are an important type of industrially-produced
single crystal A single-crystal, or monocrystalline, solid is a material in which the crystal lattice of the entire sample is continuous and unbroken to the edges of the sample, with no grain boundaries.RIWD. "Reade Advanced Materials - Single Crystals". ''ww ...
. File:Bornite-Chalcopyrite-Pyrite-180794.jpg, A specimen consisting of a bornite-coated chalcopyrite crystal nestled in a bed of clear quartz crystals and lustrous pyrite crystals. The bornite-coated crystal is up to 1.5 cm across. File:Calcite-millerite association.jpg, Needle-like millerite crystals partially encased in
calcite Image:Calcite.png, 235px, Crystal structure of calcite Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). The Mohs scale of mineral hardness, based on Scr ...

calcite
crystal and oxidized on their surfaces to zaratite; from the Devonian Milwaukee Formation of Wisconsin


See also

* Atomic packing factor * Anticrystal * Cocrystal * Colloidal crystal * Crystal growth * Crystal oscillator * Liquid crystal * Time crystal


References


Further reading

* * * * * {{Authority control Crystals,