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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 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 veins or in sedimentary rock. Agate has been popular as a gemstone in 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 Greek philosopher and naturalist. He discovered the stone c. 350 BCE along the shoreline of the River Achates (), now the Dirillo River, on the Italian ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chalcedony
Chalcedony ( or ) is a cryptocrystalline form of silica, composed of very fine intergrowths of quartz and moganite. These are both silica minerals, but they differ in that quartz has a trigonal crystal structure, while moganite is monoclinic. Chalcedony's standard chemical structure (based on the chemical structure of quartz) is SiO2 (silicon dioxide). Chalcedony has a waxy luster, and may be semitransparent or translucent. It can assume a wide range of colors, but those most commonly seen are white to gray, grayish-blue or a shade of brown ranging from pale to nearly black. The color of chalcedony sold commercially is often enhanced by dyeing or heating. The name ''chalcedony'' comes from the Latin (alternatively spelled ) and is probably derived from the town of Chalcedon in Asia Minor. The name appears in Pliny the Elder's as a term for a translucent kind of jaspis. Another reference to a gem by the name of () is found in the Book of Revelation (21:19); however, i ... [...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] |
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] |
Jewellery
Jewellery (or jewelry in American English) consists of decorative items worn for personal adornment such as brooches, ring (jewellery), rings, necklaces, earrings, pendants, bracelets, and cufflinks. Jewellery may be attached to the body or the clothes. From a western perspective, the term is restricted to durable Ornament (art), ornaments, excluding flowers for example. For many centuries metal such as gold often combined with gemstones, has been the normal material for jewellery, but other materials such as glass, shells and other plant materials may be used. Jewellery is one of the oldest types of archaeological artefact – with 100,000-year-old beads made from ''Nassarius'' shells thought to be the oldest known jewellery. The basic forms of jewellery vary between cultures but are often extremely long-lived; in European cultures the most common forms of jewellery listed above have persisted since ancient times, while other forms such as adornments for the nose or ankle, impo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quartz
Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of Silicon dioxide, SiO2. Quartz is, therefore, classified structurally as a Silicate mineral#Tectosilicates, framework silicate mineral and compositionally as an oxide mineral. Quartz is the second most abundant mineral in Earth's continental crust, behind feldspar. Quartz exists in two forms, the normal α-quartz and the high-temperature β-quartz, both of which are chiral. The transformation from α-quartz to β-quartz takes place abruptly at . Since the transformation is accompanied by a significant change in volume, it can easily induce microfracturing of ceramics or rocks passing through this temperature threshold. There are many different varieties of quartz, several of which are classifi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vein (geology)
In geology, a vein is a distinct sheetlike body of crystallized minerals within a rock. Veins form when mineral constituents carried by an aqueous solution within the rock mass are deposited through precipitation. The hydraulic flow involved is usually due to hydrothermal circulation. Veins are classically thought of as being planar fractures in rocks, with the crystal growth occurring normal to the walls of the cavity, and the crystal protruding into open space. This certainly is the method for the formation of some veins. However, it is rare in geology for significant open space to remain open in large volumes of rock, especially several kilometers below the surface. Thus, there are two main mechanisms considered likely for the formation of veins: ''open-space filling'' and ''crack-seal growth''. Open space filling Open space filling is the hallmark of epithermal vein systems, such as a stockwork, in greisens or in certain skarn environments. For open space fillin ... [...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] |
Cryptocrystalline
Cryptocrystalline is a rock microstructure, rock texture made up of such minute crystals that its crystalline nature is only vaguely revealed even microscopically in thin section by transmitted polarized light. Among the sedimentary rocks, chert and flint are cryptocrystalline. carbonado (diamond), Carbonado, a form of diamond, is also cryptocrystalline. Volcanic rocks, especially of the felsic type such as felsites and rhyolites, may have a cryptocrystalline matrix (geology), groundmass as distinguished from pure obsidian (felsic) or tachylyte (mafic), which are natural rock glasses. Agate and onyx are examples of cryptocrystalline silica (chalcedony). The quartz crystals in chalcedony are so tiny that they cannot be distinguished with the naked eye. See also * List of rock textures * Macrocrystalline * Microcrystalline * Nanocrystalline * Rock microstructure References Crystals Lithics Petrology {{Petrology-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moganite
Moganite is a tectosilicate mineral with the chemical formula Si O2 (silicon dioxide) that was discovered in 1976. It was initially described as a new form of silica from specimens found in the Barranco de Medio Almud, in the municipality of Mogán on the island of Gran Canaria, in the Canary Islands (Spain), receiving in a later work the name derived from this locality. In 1994 the International Mineralogical Association decided to disapprove it as a valid mineral, since it was considered indistinguishable from quartz. Subsequent studies allowed the IMA to rectify it in 1999, accepting it as a mineral species. It has the same chemical composition as quartz, but a different crystal structure. This mineral has been mainly found in dry locales such as Gran Canaria and Lake Magadi. It has been reported from a variety of locations in Europe, India and the United States. Physically, it has a Mohs hardness of about 6, a dull luster and appears as a semitransparent gray in color. S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Greeks
Greeks or Hellenes (; , ) are an ethnic group and nation native to Greece, Greek Cypriots, Cyprus, Greeks in Albania, southern Albania, Greeks in Turkey#History, Anatolia, parts of Greeks in Italy, Italy and Egyptian Greeks, Egypt, and to a lesser extent, other countries surrounding the Eastern Mediterranean and Black Sea. They also form a significant Greek diaspora, diaspora (), with many Greek communities established around the world.. Greek colonies and communities have been historically established on the shores of the Mediterranean Sea and Black Sea, but the Greek people themselves have always been centered on the Aegean Sea, Aegean and Ionian Sea, Ionian seas, where the Greek language has been spoken since the Bronze Age.. Until the early 20th century, Greeks were distributed between the Greek peninsula, the western coast of Asia Minor, the Black Sea coast, Cappadocia in central Anatolia, Egypt, the Balkans, Cyprus, and Constantinople. Many of these regions coincided to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Philosopher
Philosophy ('love of wisdom' in Ancient Greek) is a systematic study of general and fundamental questions concerning topics like existence, reason, knowledge, Value (ethics and social sciences), value, mind, and language. It is a rational and critical inquiry that reflects on its methods and assumptions. Historically, many of the individual sciences, such as physics and psychology, formed part of philosophy. However, they are considered separate academic disciplines in the modern sense of the term. Influential traditions in the history of philosophy include Western philosophy, Western, Islamic philosophy, Arabic–Persian, Indian philosophy, Indian, and Chinese philosophy. Western philosophy originated in Ancient Greece and covers a wide area of philosophical subfields. A central topic in Arabic–Persian philosophy is the relation between reason and revelation. Indian philosophy combines the Spirituality, spiritual problem of how to reach Enlightenment in Buddhism, enlighten ... [...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] |
