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Agates
Agate ( ) is a banded variety of chalcedony. Agate stones are characterized by alternating bands of different colored chalcedony and sometimes include Macroscopic scale, macroscopic quartz. They are common in nature and can be found globally in a large number of different varieties. There are some varieties of chalcedony without bands that are commonly called agate (moss agate, fire agate, etc.); however, these are more properly classified solely as varieties of chalcedony. Agates are primarily formed as nodules within volcanic rock, but they can also form in Vein (geology), veins or in sedimentary rock. Agate has been popular as a gemstone in Jewellery, jewelry for thousands of years, and today it is also popular as a collector's stone. Some duller agates sold commercially are artificially dyed to enhance their color. Etymology Agate was given its name by Theophrastus, a Greeks, Greek philosopher and naturalist. He discovered the stone c. 350 BCE along the shoreline of the Rive ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fire Agate
Fire agate is a variety of chalcedony that displays fire-like iridescent flashes. It is found only in certain areas of central and northern Mexico and the southwestern United States (New Mexico, Arizona and California). Despite its name, it is not a true agate, since it typically does not have bands. Approximately 24-36 million years ago, during the Tertiary Period, these areas were subjected to massive volcanic activity. Fire agates were formed when hot water, saturated with silica and iron oxide, filled cracks and cavities in the surrounding rock and solidified into chalcedony layered with crystallized iron oxide. Fire agates have beautiful iridescent rainbow colors, similar to opal. They have a hardness of 6.5-7 on the Mohs scale of mineral hardness, Mohs scale, which reduces the occurrence of scratching when polished gemstones are set in jewelry. The vibrant iridescent rainbow colors found within fire agates are created by the Schiller effect, which is also found in mother-of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moss Agate
Moss agate pebble, 1 inch (25 mm) long Moss agate is a semi-precious gemstone formed from silicon dioxide. It is a form of chalcedony which includes minerals of a green color embedded in the stone, forming filaments and other patterns suggestive of moss. The field is a clear or milky-white quartz, and the included minerals are mainly oxides of manganese or iron. It is not a true form of agate, because it does not have concentric banding. Moss agate can be clear or milky white, with green dendritic inclusions that resemble moss. The colors are formed due to trace amounts of metal present as an impurity, such as chrome or iron. The metals can make different colors depending on their valence (oxidation state). Despite its name, moss agate does not contain organic matter and is usually formed from weathered volcanic rocks. Moss agate is found in countries across the world, including India, Brazil, Uruguay, central European countries, and the United States. In the U.S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tectosilicate
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 dioxide, ) are usually considered to be tectosilicates, and they are classified as such in the Dana system (75.1). However, the Nickel-Strunz system classifies them as oxide minerals (4.DA). Silica is found in nature as the mineral quartz, and its polymorphs. On Earth, a wide variety of silicate minerals occur in an even wider range of combinations as a result of the processes that have been forming and re-working the crust for billions of years. These processes include partial melting, crystallization, fractionation, metamorphism, weathering, and diagenesis. Living organisms also contribute to this geologic cycle. For example, a type of plankton known as diatoms construct their exoskeletons ("frustules") from silica extracted from sea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 as lapis lazuli, opal, and obsidian) and occasionally organic chemistry, organic materials that are not minerals (such as amber, Jet (gemstone), jet, and pearl) may also be used for jewelry and are therefore often considered to be gemstones as well. Most gemstones are hard, but some softer minerals such as brazilianite may be used in jewelry because of their color or Lustre (mineralogy), luster or other physical properties that have aesthetic value. However, generally speaking, soft minerals are not typically used as gemstones by virtue of their brittleness and lack of durability. Found all over the world, the industry of coloured gemstones (i.e. anything other than diamonds) is currently estimated at US$1.55billion and is projected to s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Andesite
Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predominantly of sodium-rich plagioclase plus pyroxene or hornblende. Andesite is the extrusive equivalent of plutonic diorite. Characteristic of subduction zones, andesite represents the dominant rock type in island arcs. The average composition of the continental crust is andesitic. Along with basalts, andesites are a component of the Geology of Mars, Martian crust. The name ''andesite'' is derived from the Andes mountain range, where this rock type is found in abundance. It was first applied by Christian Leopold von Buch in 1826. Description Andesite is an aphanitic (fine-grained) to porphyritic (coarse-grained) igneous rock that is intermediate in its content of silica and low in alkali metals. It has less than 20% quartz and 10% feldspa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Basalt
Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial planet, rocky planet or natural satellite, moon. More than 90% of all volcanic rock on Earth is basalt. Rapid-cooling, fine-grained basalt is chemically equivalent to slow-cooling, coarse-grained gabbro. The eruption of basalt lava is observed by geologists at about 20 volcanoes per year. Basalt is also an important rock type on other planetary bodies in the Solar System. For example, the bulk of the plains of volcanism on Venus, Venus, which cover ~80% of the surface, are basaltic; the lunar mare, lunar maria are plains of flood-basaltic lava flows; and basalt is a common rock on the surface of Mars. Molten basalt lava has a low viscosity due to its relatively low silica content (between 45% and 52%), resulting in rapidly moving lava flo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nodule (geology)
In geology and particularly in sedimentology, a nodule is a small, irregularly rounded knot, mass, or lump of a mineral or mineral aggregate that typically has a contrasting composition from the enclosing sediment or sedimentary rock. Examples include pyrite nodules in coal, a chert nodule in limestone, or a phosphorite nodule in marine shale. Normally, a nodule has a warty or knobby surface and exists as a discrete mass within the host strata. In general, they lack any internal structure except for the preserved remnants of original bedding or fossils. Nodules are closely related to '' concretions'' and sometimes these terms are used interchangeably. Minerals that typically form nodules include calcite, chert, apatite (phosphorite), anhydrite, and pyrite.Neuendorf, KKE, JP Mehl, Jr., and JA Jackson, eds. (2005) ''Glossary of Geology'' (5th ed.). Alexandria, Virginia, American Geological Institute. 779 pp. Boggs S, Jr. (2009) ''Petrology of Sedimentary Rocks.'' Cambridge Univ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sicily
Sicily (Italian language, Italian and ), officially the Sicilian Region (), is an island in the central Mediterranean Sea, south of the Italian Peninsula in continental Europe and is one of the 20 regions of Italy, regions of Italy. With 4.7 million inhabitants, including 1.2 million in and around the capital city of Palermo, it is both the largest and most populous island in the Mediterranean Sea. Sicily is named after the Sicels, who inhabited the eastern part of the island during the Iron Age. Sicily has a rich and unique culture in #Art and architecture, arts, Music of Sicily, music, #Literature, literature, Sicilian cuisine, cuisine, and Sicilian Baroque, architecture. Its most prominent landmark is Mount Etna, the tallest active volcano in Europe, and one of the most active in the world, currently high. The island has a typical Mediterranean climate. It is separated from Calabria by the Strait of Messina. It is one of the five Regions of Italy#Autonomous regions with s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Italy
Italy, officially the Italian Republic, is a country in Southern Europe, Southern and Western Europe, Western Europe. It consists of Italian Peninsula, a peninsula that extends into the Mediterranean Sea, with the Alps on its northern land border, as well as List of islands of Italy, nearly 800 islands, notably Sicily and Sardinia. Italy shares land borders with France to the west; Switzerland and Austria to the north; Slovenia to the east; and the two enclaves of Vatican City and San Marino. It is the List of European countries by area, tenth-largest country in Europe by area, covering , and the third-most populous member state of the European Union, with nearly 59 million inhabitants. Italy's capital and List of cities in Italy, largest city is Rome; other major cities include Milan, Naples, Turin, Palermo, Bologna, Florence, Genoa, and Venice. The history of Italy goes back to numerous List of ancient peoples of Italy, Italic peoples—notably including the ancient Romans, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dirillo
The Dirillo, or Acate, is a river in Sicily which springs from the Hyblaean Mountains and flows through the areas of Vizzini, Licodia Eubea, Mazzarrone, Chiaramonte Gulfi, Acate, Vittoria, Gela. It enters the Strait of Sicily south-east of the town of Gela. As the largest river in the area it is sometimes known as the ''Fiume Grande''. The river was known in antiquity as the Achates (). It was noted by Silius Italicus for the remarkable clearness of its waters. Theophrastus in his treatise '' On Stones'' (ca. 315 B.C.) indicates that the name of the gemstone ''achates'' (agate) was based on the source of such stones from this river. Pliny the Elder makes the same connection in his ''Naturalis Historia'' at the [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Naturalist
Natural history is a domain of inquiry involving organisms, including animals, fungi, and plants, in their natural environment, leaning more towards observational than experimental methods of study. A person who studies natural history is called a naturalist or natural historian. Natural history encompasses scientific research but is not limited to it. It involves the systematic study of any category of natural objects or organisms, so while it dates from studies in the ancient Greco-Roman world and the mediaeval Arabic world, through to European Renaissance naturalists working in near isolation, today's natural history is a cross-discipline umbrella of many specialty sciences; e.g., geobiology has a strong multidisciplinary nature. Definitions Before 1900 The meaning of the English term "natural history" (a calque of the Latin ''historia naturalis'') has narrowed progressively with time, while, by contrast, the meaning of the related term "nature" has widened (see also ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
