Topaz (Ruby)
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Topaz is a
silicate mineral Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, the crystalline forms of silica (silicon dio ...
made of
aluminum Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...
and
fluorine Fluorine is a chemical element; it has Chemical symbol, symbol F and atomic number 9. It is the lightest halogen and exists at Standard temperature and pressure, standard conditions as pale yellow Diatomic molecule, diatomic gas. Fluorine is extre ...
with the
chemical formula A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...
Al Si O( F, OH). It is used as a
gemstone A gemstone (also called a fine gem, jewel, precious stone, semiprecious stone, or simply gem) is a piece of mineral crystal which, when cut or polished, is used to make jewellery, jewelry or other adornments. Certain Rock (geology), rocks (such ...
in jewelry and other adornments. Common topaz in its natural state is colorless, though trace element impurities can make it pale blue or golden-brown to yellow-orange. Topaz is often treated with heat or radiation to make it a deep blue, reddish-orange, pale green, pink, or purple. Topaz is a
nesosilicate Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, the crystalline forms of silica (silicon dio ...
mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...
, and more specifically, an aluminosilicate mineral. It is one of the hardest naturally occurring minerals and has a relatively low
index of refraction In optics, the refractive index (or refraction index) of an optical medium is the ratio of the apparent speed of light in the air or vacuum to the speed in the medium. The refractive index determines how much the path of light is bent, or refrac ...
. It has the orthorhombic
crystal system In crystallography, a crystal system is a set of point groups (a group of geometric symmetries with at least one fixed point). A lattice system is a set of Bravais lattices (an infinite array of discrete points). Space groups (symmetry groups ...
and a dipyramidial
crystal class In crystallography, a crystallographic point group is a three-dimensional point group whose symmetry operations are compatible with a three-dimensional crystallographic lattice. According to the crystallographic restriction it may only contain on ...
. It occurs in many places in the world. Some of the most popular places where topaz is sourced are Brazil and Russia. Topaz is often mined in open pit or alluvial settings.


Etymology

The word "topaz" is usually believed to be derived (via
Old French Old French (, , ; ) was the language spoken in most of the northern half of France approximately between the late 8th -4; we might wonder whether there's a point at which it's appropriate to talk of the beginnings of French, that is, when it wa ...
: Topace and Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...
''Τοπάζιος'' (Topázios) or ''Τοπάζιον'' (Topázion), from Τοπαζος. This is the ancient name of St. John's Island in the Red Sea">St. John's Island, Egypt">St. John's Island in the chrysolite: yellowish olivine">Red Sea which was difficult to find and from which a yellow stone (now believed to be Peridot">chrysolite: yellowish olivine) was mined in ancient times. The name ''topaz'' was first applied to the mineral now known by that name in 1737. Ancient Sri Lanka (Tamraparni) exported topazes to Greece and ancient Egypt, which led to the etymologically related names of the island by Alexander Polyhistor (''Topazius'') and the early Egyptians (''Topapwene'') – "land of the Topaz". Pliny said that Topazos is a ''legendary'' island in the
Red Sea The Red Sea is a sea inlet of the Indian Ocean, lying between Africa and Asia. Its connection to the ocean is in the south, through the Bab-el-Mandeb Strait and the Gulf of Aden. To its north lie the Sinai Peninsula, the Gulf of Aqaba, and th ...
and the mineral "topaz" was first mined there. Alternatively, the word ''topaz'' may be related to the Sanskrit word तपस् "tapas", meaning "heat" or "fire".


History

Thomas Nicols, the author of one of the first systematic treatises on minerals and gemstones, dedicated two chapters to the topic in 1652. In the
Middle Ages In the history of Europe, the Middle Ages or medieval period lasted approximately from the 5th to the late 15th centuries, similarly to the post-classical period of global history. It began with the fall of the Western Roman Empire and ...
, the name topaz was used to refer to any yellow gemstone, but in modern times it denotes only the silicate described above. Many English translations of the
Bible The Bible is a collection of religious texts that are central to Christianity and Judaism, and esteemed in other Abrahamic religions such as Islam. The Bible is an anthology (a compilation of texts of a variety of forms) originally writt ...
, including the
King James Version The King James Version (KJV), also the King James Bible (KJB) and the Authorized Version (AV), is an Early Modern English Bible translations, Early Modern English translation of the Christianity, Christian Bible for the Church of England, wh ...
, mention topaz. However, because these translations as ''topaz'' all derive from the
Septuagint The Septuagint ( ), sometimes referred to as the Greek Old Testament or The Translation of the Seventy (), and abbreviated as LXX, is the earliest extant Greek translation of the Hebrew Bible from the original Biblical Hebrew. The full Greek ...
translation ''topazi s', which referred to a yellow stone that was not topaz, but probably ''chrysolite'' (
chrysoberyl The mineral or gemstone chrysoberyl is an aluminate of beryllium with the formula Be Al2 O4. The name chrysoberyl is derived from the Greek words χρυσός ''chrysos'' and βήρυλλος ''beryllos'', meaning "a gold-white spar". Despit ...
or
peridot Peridot ( ), sometimes called chrysolite, is a yellow-green transparent variety of olivine. Peridot is one of the few gemstones that occur in only one color. Peridot can be found in mafic and ultramafic rocks occurring in lava and peridotite ...
), topaz is likely not meant here. An English superstition also held that topaz cured lunacy. The ancient Romans believed that topaz provided protection from danger while traveling. During the Middle Ages, it was believed that attaching the topaz to the left arm protected the owner from any curse and warded off the
evil eye The evil eye is a supernatural belief in a curse brought about by a malevolent glaring, glare, usually inspired by envy. Amulets to Apotropaic, protect against it have been found dating to around 5,000 years ago. It is found in many cultures i ...
. It was also believed that wearing topaz increased body heat, which would enable people to relieve a cold or fever. In Europe during the Middle Ages, topaz was believed to enhance mental powers. In India, people believed topaz granted beauty, intelligence, and longevity when worn over the heart.


Gemstone

Topaz is a
gemstone A gemstone (also called a fine gem, jewel, precious stone, semiprecious stone, or simply gem) is a piece of mineral crystal which, when cut or polished, is used to make jewellery, jewelry or other adornments. Certain Rock (geology), rocks (such ...
. In cut and polished form, it is used to make jewelry or other adornments. Lower quality topaz is commonly used as an
abrasive An abrasive is a material, often a mineral, that is used to shape or finish a workpiece through rubbing which leads to part of the workpiece being worn away by friction. While finishing a material often means polishing it to gain a smooth, reflec ...
material due to its hardness and it is used to produce
refractory In materials science, a refractory (or refractory material) is a material that is resistant to decomposition by heat or chemical attack and that retains its strength and rigidity at high temperatures. They are inorganic, non-metallic compound ...
materials for high temperature environments. Topaz can be used as a flux in steel production. Using topaz as a refectory material does have some health and environmental concerns due to the production of fluorine as a byproduct of calcining topaz. Topaz is a part of the second rank of gemstones, or semiprecious stones, accompanying aquamarine,
morganite Morganite is an orange or pink variety of beryl and is also a gemstone. Morganite is mined in Brazil, Afghanistan, Mozambique, Namibia, the United States, and Madagascar. Morganite has grown in popularity since 2010. '' Brides'' and CNN have li ...
, and
tourmaline Tourmaline ( ) is a crystalline silicate mineral, silicate mineral group in which boron is chemical compound, compounded with chemical element, elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. This gemstone comes in a ...
. The first rank of gemstones, or precious stones, includes
ruby Ruby is a pinkish-red-to-blood-red-colored gemstone, a variety of the mineral corundum ( aluminium oxide). Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called sapph ...
,
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, cobalt, lead, chromium, vanadium, magnesium, boron, and silicon. The name ''sapphire ...
,
diamond Diamond is a Allotropes of carbon, solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Diamond is tasteless, odourless, strong, brittle solid, colourless in pure form, a poor conductor of e ...
, and
emerald Emerald is a gemstone and a variety of the mineral beryl (Be3Al2(SiO3)6) colored green by trace amounts of chromium or sometimes vanadium.Hurlbut, Cornelius S. Jr., and Kammerling, Robert C. (1991). ''Gemology'', John Wiley & Sons, New York ...
. Orange topaz, also known as precious topaz, is the
birthstone A birthstone is a gemstone that represents a person's birth period, usually the month or zodiac sign. Birthstones are often worn as jewelry or a pendant necklace. History of birthstones Western custom The first-century historian Josephus bel ...
for the month of November, the symbol of friendship, and the
state gemstone Leaders of states in the U.S. which have significant mineral deposits often create a state mineral, rock, stone or gemstone to promote interest in their natural resources, history, tourism, etc. Not every state has an official state mineral, rock, ...
of the U.S. state of
Utah Utah is a landlocked state in the Mountain states, Mountain West subregion of the Western United States. It is one of the Four Corners states, sharing a border with Arizona, Colorado, and New Mexico. It also borders Wyoming to the northea ...
. Blue topaz is the state gemstone of the US state of
Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...
. The 4th wedding anniversary gem is blue topaz and the 23rd is imperial topaz. Synthetic topaz can be produced using a method that includes the thermal hydrolysis of SiO2 and AlF3. When these compounds are heated to temperatures of 750° to 850 °C topaz is formed. Another method uses a combination of amorphous Al2O3, Na2SiF6, and water which is heated to a temperature of 500 °C, put under a pressure of 4000 bars, and left for 9 days. To care for a topaz gemstone, it is best to avoid ultrasonic cleaners or steam as this could produce small fractures within the crystal. Warm water with soap is the best way to wash it. To choose an ethically sourced topaz gemstone, it is recommended to search for a stone that the seller knows the origin of. If the seller cannot produce information about the locality and mine that the topaz was collected from, it is likely that it was collected unethically.


Structure

Topaz is an accessory mineral to felsic igneous, sedimentary, and hydrothermally altered rocks. The crystal structure of topaz alternates between sheets of (F, OH)2O and O along (010) with Al3+ occupying the octahedral sites and Si4+ in the tetrahedral sites. Fluorine can be substituted by hydroxide in topaz by up to 30 mol.% in nature and hydroxide-dominating topaz can be made in laboratories but has not been found in nature. On occasion, cavities can be found within topaz and they are filled with a liquid called brewsterlinite. Brewsterlinite was discovered by
David Brewster Sir David Brewster Knight of the Royal Guelphic Order, KH President of the Royal Society of Edinburgh, PRSE Fellow of the Royal Society of London, FRS Fellow of the Society of Antiquaries of Scotland, FSA Scot Fellow of the Scottish Society of ...
upon heating a sample of topaz. After heating, the topaz lost mass, and through examination Brewster concluded Topaz was formed in a wet environment creating these liquid-filled cavities. This liquid is a hydrocarbon with a refractive index of 1·13. Topaz's crystal habit takes many forms. It can display a range of slender and long crystals to bulky and short. There can also be variation in the terminations displaying blunt, pyramidal, chisel, or wedge-shaped terminations. The perfect cleavage in topaz breaks no Si-O bonds within its structure and only breaks Al-O and Al-F bonds. This cleavage is diagnostic for this mineral. The 2V optical angle in topaz can range from 48° to 69.5°. Low fluorine content yields a smaller angle and high fluorine content yields a larger angle.


Characteristics

Topaz in its natural state is colorless, often with a greyish cast. It also occurs as a golden brown to yellow color which makes it sometimes confused with citrine, a less valuable gemstone. The
specific gravity Relative density, also called specific gravity, is a dimensionless quantity defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for solids and liquids is nea ...
of all shades of topaz, however, means that it is considerably heavier than citrine (about 25% per volume) and this difference in weight can be used to distinguish two stones of equal volume. Also, if the volume of a given stone can be determined, its weight if it were topaz can be established and then checked with a sensitive scale. Likewise, glass stones are also much lighter than equally sized topaz. A variety of impurities and treatments may make topaz wine red, pale gray, reddish-orange, pale green, or pink (rare), and opaque to translucent/transparent. The pink and red varieties come from chromium replacing aluminium in its crystalline structure. Imperial topaz is yellow, pink (rare, if natural), or pink-orange. Brazilian imperial topaz can often have a bright yellow to deep golden brown hue, sometimes even violet. Many brown or pale topazes are treated to make them bright yellow, gold, pink, or violet colored. Some imperial topaz stones can fade from exposure to sunlight for an extended period of time. Naturally occurring blue topaz is quite rare. Typically, colorless, gray, or pale yellow and blue material is heat treated and
irradiated Irradiation is the process by which an object is exposed to radiation. An irradiator is a device used to expose an object to radiation, most often gamma radiation, for a variety of purposes. Irradiators may be used for sterilizing medical and p ...
to produce a more desired darker blue. Mystic topaz is a colorless topaz that has been artificially coated via a
vapor deposition Vacuum deposition is a group of processes used to deposit layers of material atom-by-atom or molecule-by-molecule on a solid surface. These processes operate at pressures well below atmospheric pressure (i.e., vacuum). The deposited layers can r ...
process giving it a rainbow effect on its surface. Although very hard, topaz must be treated with greater care than some other minerals of similar hardness (such as
corundum Corundum is a crystalline form of aluminium oxide () typically containing traces of iron, titanium, vanadium, and chromium. It is a rock (geology), rock-forming mineral. It is a naturally transparency and translucency, transparent material, but ...
) because of a weakness of atomic bonding of the stone's molecules along one or another axial plane (whereas diamonds, for example, are composed of carbon atoms bonded to each other with equal strength along all of its planes). This gives topaz a tendency to break along such a cleavage plane if struck with sufficient force. Topaz has a relatively low
index of refraction In optics, the refractive index (or refraction index) of an optical medium is the ratio of the apparent speed of light in the air or vacuum to the speed in the medium. The refractive index determines how much the path of light is bent, or refrac ...
for a gemstone, and so stones with large facets or tables do not sparkle as readily as stones cut from minerals with higher refractive indices, though quality colorless topaz sparkles and shows more "life" than similarly cut quartz. When given a typical "brilliant" cut, topaz may either show a sparkling table facet surrounded by dead-looking crown facets or a ring of sparkling crown facets with a dull well-like table. It also takes an exceptionally fine polish, and can sometimes be distinguished from citrine by its slippery feel alone (quartz cannot be polished to this level of smoothness). Another method of distinguishing topaz from quartz is by placing the unset stone in a solution of
bromoform Bromoform is an organic compound with the chemical formula . It is a colorless liquid at room temperature, with a high refractive index and a very high density. Its sweet odor is similar to that of chloroform. It is one of the four haloforms, the ...
or
methylene iodide Diiodomethane or methylene iodide, commonly abbreviated "MI", is an organoiodine compound. Diiodomethane is a very dense colorless liquid; however, it decomposes upon exposure to light liberating iodine, which colours samples brownish. It is slig ...
. Quartz will invariably float in these solutions, whereas topaz will sink.


Localities and occurrence

Topaz is commonly associated with
silicic Silicic is an adjective to describe magma or igneous rock rich in silica. The amount of silica that constitutes a silicic rock is usually defined as at least 63 percent. Granite and rhyolite are the most common silicic rocks. Silicic is the g ...
igneous rocks of the
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 coo ...
and
rhyolite Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture (geology), texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained matri ...
type. It typically crystallizes in granitic
pegmatites A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than and sometimes greater than . Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic com ...
or in vapor cavities in rhyolite lava flows including those at Topaz Mountain in western Utah and Chivinar in South America. It can be found with
fluorite Fluorite (also called fluorspar) is the mineral form of calcium fluoride, CaF2. It belongs to the halide minerals. It crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon. The Mohs scal ...
and
cassiterite Cassiterite is a tin oxide mineral, SnO2. It is generally opaque, but it is translucent in thin crystals. Its luster and multiple crystal faces produce a desirable gem. Cassiterite was the chief tin ore throughout ancient history and remains ...
in various areas including the Ural and Ilmensky mountains of Russia, Afghanistan, Sri Lanka, the Czech Republic, Germany, Norway, Pakistan, Italy, Sweden, Japan, Brazil, Mexico;
Flinders Island Flinders Island, the largest island in the Furneaux Group, is a island in the Bass Strait, northeast of the island of Tasmania. Today Flinders Island is part of the state of Tasmania, Australia. It is from Cape Portland, Tasmania, Cape Portl ...
, Australia; Nigeria, Ukraine and the United States. Topaz was found around the time of the 1700s in a pegmatite formation within the central Urals Mountains in Russia. Brazil is one of the largest producers of topaz, some clear topaz crystals from Brazilian pegmatites can reach boulder size and weigh hundreds of pounds. The Topaz of
Aurangzeb Alamgir I (Muhi al-Din Muhammad; 3 November 1618 – 3 March 1707), commonly known by the title Aurangzeb, also called Aurangzeb the Conqueror, was the sixth Mughal emperors, Mughal emperor, reigning from 1658 until his death in 1707, becomi ...
, observed by Jean Baptiste Tavernier weighed . The
American Golden Topaz The American Golden Topaz, a 172-faceted topaz weighing , is the largest cut yellow topaz in the world, and one of the largest faceted Gemstone, gems of any type in the world. Originating from Minas Gerais, Brazil, it was cut by Leon Agee over a p ...
, a more recent gem, weighed . Large, vivid blue topaz specimens from the St. Anns mine in
Zimbabwe file:Zimbabwe, relief map.jpg, upright=1.22, Zimbabwe, relief map Zimbabwe, officially the Republic of Zimbabwe, is a landlocked country in Southeast Africa, between the Zambezi and Limpopo Rivers, bordered by South Africa to the south, Bots ...
were found in the late 1980s. Colorless and light-blue varieties of topaz are found in
Precambrian The Precambrian ( ; or pre-Cambrian, sometimes abbreviated pC, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of t ...
granite in
Mason County, Texas Mason County is a rural county located on the Edwards Plateau in the U.S. state of Texas. At the 2020 census, its population was 3,953. Its county seat is Mason. The county is named for Fort Mason, which was located in the county. History ...
within the
Llano Uplift The Llano Uplift is a geologically ancient, low geologic dome that is about in diameter and located mostly in Llano, Mason, San Saba, Gillespie, and Blanco counties, Texas. It consists of an island-like exposure of Precambrian igneous and ...
. There is no commercial mining of topaz in that area. It is possible to synthesize topaz.


Mining

Large-scale topaz mining typically uses
open pit Open-pit mining, also known as open-cast or open-cut mining and in larger contexts mega-mining, is a surface mining technique that extracts rock or minerals from the earth. Open-pit mines are used when deposits of commercially useful ore or ...
and underground mining to extract the gem. The waste material is discarded using large machines to transport it away while the valuable ore is washed and sorted to recover the topaz gems. In smaller-scale mines, dry sieving is used in
alluvial Alluvium (, ) is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluvium is also sometimes called alluvial deposit. Alluvium is ...
environments by shoveling the material into sieves to separate the gems from unwanted dust and debris. The topaz can then be selected by hand from the remaining material. Mined topaz is then sent to be processed for use in jewelry by polishing the gem and treating it to achieve the desired color. Mining for topaz can cause some environmental concerns mostly associated with larger-scale operations. The introduction of a large open pit mine into an environment leads to modification of the land around it to make it accessible to workers. After use of such mines is over, they are often refilled with loose sediments left over from the mining process. These loose sediments can be washed away to other areas, cutting off water features, destroying farmland, and creating a threat of
landslides Landslides, also known as landslips, rockslips or rockslides, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, mudflows, shallow or deep-seated slope failures and debris flows. Landslide ...
. The pollution produced by mining can impact the environment around it and damage its health.
Deforestation Deforestation or forest clearance is the removal and destruction of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. Ab ...
undergone to create the mine, along with the machinery used during the mining process, adds
greenhouse gasses Greenhouse gases (GHGs) are the gases in the atmosphere that raise the surface temperature of planets such as the Earth. Unlike other gases, greenhouse gases absorb the radiations that a planet emits, resulting in the greenhouse effect. T ...
to the atmosphere. Deforestation also removes habitats and
biodiversity Biodiversity is the variability of life, life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and Phylogenetics, phylogenetic diversity. Diversity is not distribut ...
from a large area of natural space. These disruptions to the ecosystem can be challenging to wildlife and local populations. Water, also a large component of mining operations, is drawn away from neighboring communities to create a lack of water.
Tailings In mining, tailings or tails are the materials left over after the process of separating the valuable fraction from the uneconomic fraction (gangue) of an ore. Tailings are different from overburden, which is the waste rock or other material ...
leftover from the mining process can leach contaminants into nearby water systems and can contaminate the drinking water of local communities. Some ways humans can be impacted by gem mining is through danger in mines and inadequate compensation. Accidents such as collapsing mines and machinery malfunctioning can put human life in danger. Those working in the mines can also be exposed to harmful chemicals and
heavy metals upright=1.2, Crystals of lead.html" ;"title="osmium, a heavy metal nearly twice as dense as lead">osmium, a heavy metal nearly twice as dense as lead Heavy metals is a controversial and ambiguous term for metallic elements with relatively h ...
that can impact their health. For income, there can be an unequal dispersal of the funds made from gem mining between land owners, laborers, and the operators of the mine. In illegal mining operations, there can be more money given to miners, however, these operations have fewer regulations and more dangerous environments. File:TopazMountainByPhilKonstantin.jpg, Topaz Mountain, Utah, United States File:Topaz-200562.jpg, Red topaz from Tepetate, Municipio de Villa de Arriaga, San Luis Potosí, Mexico File:Large Topaz Gemstones.jpg, Facet cut topaz gemstones in various colors File:YellowTopaz.jpeg, Yellow topaz in stepped kite-shaped cut File:TOPAZE9.jpg, Imperial Topaz of Minas Gerais


See also

*
Agate Agate ( ) is a banded variety of chalcedony. Agate stones are characterized by alternating bands of different colored chalcedony and sometimes include macroscopic quartz. They are common in nature and can be found globally in a large number of d ...
*
Beryl Beryl ( ) is a mineral composed of beryllium aluminium Silicate minerals#Cyclosilicates, silicate with the chemical formula Be3Al2(SiO3)6. Well-known varieties of beryl include emerald and Aquamarine (gem), aquamarine. Naturally occurring Hex ...
*
Opal Opal is a hydrated amorphous form of silicon dioxide, silica (SiO2·''n''H2O); its water content may range from 3% to 21% by weight, but is usually between 6% and 10%. Due to the amorphous (chemical) physical structure, it is classified as a ...


References


External links


Topaz
from the International Colored Gemstone Association

Utah Geological Survey * {{Authority control Aluminium minerals Gemstones Nesosilicates Orthorhombic minerals Minerals in space group 62 Luminescent minerals