Quartz varieties Quartz varieties Agate is a term applied not to a distinct mineral species, but to an aggregate of various forms of silica, chiefly chalcedony. ...more on Wikipedia about "Agate"
Amethyst (SiO2) is a violet or purple variety of quartz often used as an ornament. The name is generally said to be derived from the Greek a, "not," and methuskein, "to intoxicate," expressing the old belief that the stone protected its owner from drunkenness. It was held that wine drunk out of a cup of amethyst would not intoxicate. However, the word may probably be a corruption of an Oriental name for the stone. ...more on Wikipedia about "Amethyst"
Ametrine, also known as Trystine, is a naturally occurring variety of quartz. It is a mixture of amethyst and citrine with zones of purple and yellow or orange. Almost all commercially available ametrine is mined in Bolivia, although there are deposits being exploited in Brazil and India. ...more on Wikipedia about "Ametrine"
Aventurine is a form of quartz, characterised by its translucency and the presence of platy mineral occlusions that give a shimmering or glistening effect termed aventurescence. The most common colour of aventurine is green, but it may also be orange, brown, yellow, blue or gray. ...more on Wikipedia about "Aventurine"
Cairngorm is a variety of quartz crystal originally found in the Cairngorm Mountains of Scotland. It usually has a smokey yellow-brown colour, though some specimens are a grey-brown. Like other quartz gems, it is a silicon dioxide crystal, with a small amount of ferric oxide impurity which gives it the characteristic colour. ...more on Wikipedia about "Cairngorm"
Carnelian is a red or reddish-brown variant of chalcedony. The word is derived from the Latin word meaning flesh, in reference to the flesh color sometimes exhibited. ...more on Wikipedia about "Carnelian"
Chalcedony is one of the cryptocrystalline varieties of the mineral quartz, having a waxy luster. Chalcedony may be semitransparent or translucent and is usually white to gray, grayish-blue or some shade of brown, sometimes nearly black. Other shades have been given different names. A clear red chalcedony is known as carnelian or sard; a green variety colored by nickel oxide is called chrysoprase. Prase is a dull green and onyx is black and white banded. Plasma is a bright to emerald-green chalcedony that is sometimes found with small spots of jasper resembling blood drops; it has been referred to as blood stone or heliotrope. Chalcedony is one of the few minerals other than quartz that is found in geodes. ...more on Wikipedia about "Chalcedony"
Chrysoprase (also chrysophrase) is a gemstone variety of chalcedony (fibrous form of quartz) that contains small quantities of nickel. Its color is normally apple-green, but varies to deep green. It is cryptocrystalline, which means that it is composed of crystals so fine that they cannot be seen as distinct particles under normal magnification. This sets it apart from rock crystal, amethyst, citrine, and the other varieties of crystalline quartz which are basically transparent and formed from easily recognized six-sided crystals. Other members of the cryptocrystalline quartz family include agate, carnelian, and onyx. Unlike many non-transparent members of the quartz family, it is the color of chrysoprase, rather than any pattern of markings, that makes it desirable. ...more on Wikipedia about "Chrysoprase"
Citrine, also called citrine quartz or citrine topaz, is an amber-coloured gemstone. It is a form of quartz with ferric iron impurities, and is rarely found naturally. Most commercial citrine is in fact artificially heated amethyst or smoky quartz. Brazil is the leading producer of naturally mined citrine, with much of its production coming from the state of Rio Grande do Sul. ...more on Wikipedia about "Citrine"
Coesite is a form of silicon dioxide that is formed when very high pressure (2–3 gigapascals) and moderately high temperature (700 °C) are applied to quartz. Coesite was first created by Loren Coes in 1953. In 1960, coesite was found by Eugene Shoemaker to naturally occur in the Barringer Crater, which was evidence that the crater must have been formed by an impact. ...more on Wikipedia about "Coesite"
Common in volcanic rocks, cristobalite is a high-temperature polymorph of quartz and tridymite. It occurs as white octahedra in acidic volcanic rocks. Cristobalite is stable only above 1470 degrees Celsius (American Geological Institute Dictionary of Geological Terms). ...more on Wikipedia about "Cristobalite"
A Mexican agate, showing only a single eye, has received the name of cyclops. Included matter of a green colour, like fragments of "green earth," embedded in the chalcedony and disposed in filaments and other forms suggestive of vegetable growth, gives rise to moss agate. ...more on Wikipedia about "Cyclops (rock)"
Jasper is an opaque, impure variety of quartz that is usually red, yellow or brown in color. This mineral breaks with a smooth surface, and is often used for ornamentation or as a gemstone. It can be highly polished and is used for vases, seals, and at one time for snuff boxes. When the colors are in stripes or bands, it is called striped or banded jasper. Jaspilite is a banded iron formation rock that often has distinctive bands of jasper. The Egyptian pebble is a brownish-yellow jasper. ...more on Wikipedia about "Jasper"
Menilite is a reddish-brown form of opal, also known as "liver" opal or leberopal. ...more on Wikipedia about "Menilite" It's my http://www.shortopedia.com!
Milk quartz or Milky quartz is probably the most common variety of quartz and can be found almost anywhere. The white colour is caused by inclusions of minute gas bubbles and/or water. ...more on Wikipedia about "Milk quartz"
Morion or morion quartz is a dark- brown to black opaque variety of smoky quartz resulting from the natural or artificial irradiation of aluminium-containing milk quartz. ...more on Wikipedia about "Morion"
Moss agate is a semi-precious gemstone formed from silica. It is a form of agate which includes minerals of a green colour embedded in the chalcedony, 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. ...more on Wikipedia about "Moss agate"
Onyx is a banded variety of chalcedony, a cryptocrystalline form of quartz. The colors of its bands are white and black. ...more on Wikipedia about "Onyx"
The mineraloid opal is amorphous SiO2·nH2O; hydrated silicon dioxide, the water content sometimes being as high as 20%. Opal ranges from colorless through white, milky blue, gray, red, yellow, green, brown and black. Often many of these colors can be seen at once, caused by interference and diffraction of light passing through minute, regularly arranged apertures within the microstructure of opal, known as Bragg's lattice. These apertures are filled with secondary silica and form thin lamellae inside the opal during solidification. The term opalescence is commonly and erroneously used to describe this unique and beautiful phenomenon, which is correctly termed play of color. Contrarily, opalescence is correctly applied to the milky, turbid appearance of common or potch opal. Potch does not show a play of color. ...more on Wikipedia about "Opal"
Petrified wood is a type of fossil: it exists of fossil wood where all the organic materials have been replaced with minerals (most often a silicate, such as quartz), while retaining the original structure of the wood. The petrifaction process has occurred underground, when wood became buried under sediment. Mineral-rich water flowing through the sediment deposited minerals in the plant's cells and as the plant's lignin and cellulose decayed away, a stone cast was formed in its place. ...more on Wikipedia about "Petrified wood"
Prase is a green translucent chalcedony (quartz). It gets its coloring from chlorite and hornblende and has been used for engravings since antiquity. ...more on Wikipedia about "Prase" Enjoy http://www.shortopedia.com.
Prasiolite or vermarine is a green-colored form of quartz, usually produced by artificially heat-treating amethyst. Since 1950, almost all has come from one small mine in Brazil. Natural prasiolite has also been obeserved in Lower Silesia in Poland. ** The gem has a refractive index of about 1.54-1.553. ** ...more on Wikipedia about "Prasiolite"
Quartz is the most abundant mineral in the Earth's continental crust. It has a hexagonal crystal structure made of trigonal crystallized silica (silicon dioxide, SiO2), with a hardness of 7 on the Mohs scale. Density is 2.65 g/cm³. The typical shape is a six-sided prism that ends in six-sided pyramids, although these are often twinned, distorted, or so massive that only part of the shape is apparent from a mined specimen. Additionally a bed is a common form, particularly for varieties such as amethyst, where the crystals grow up from a matrix and thus only one termination pyramid is present. A quartz geode consists of a hollow rock (usually with an approximately spherical shape) with a core lined with a bed of crystals. ...more on Wikipedia about "Quartz"
Quartz-porphyry, in petrology, is the name given to a group of hemi- crystalline acid rocks containing porphyritic crystals of quartz in a more fine-grained matrix which is usually of micro-crystalline or felsitic structure. In the hand specimens the quartz appears as small rounded, clear, greyish, vitreous blebs, which are crystals, double hexagonal pyramids, with their edges and corners rounded by resorption or corrosion. Under the microscope they are often seen to contain rounded enclosures of the ground-mass or fluid cavities, which are frequently negative crystals with regular outlines resembling those of perfect quartz crystals. ...more on Wikipedia about "Quartz-porphyry"
Rose quartz is a type of quartz which exhibits a pale pink to rose red hue. The color is usually considered as due to trace amounts of titanium, iron, or manganese, in the massive material. Some rose quartz contains microscopic rutile needles which produces an asterism in transmitted light. Recent X-ray diffraction studies suggest that the color is due to thin microscopic fibers of possibly dumortierite within the massive quartz. It is rarely found in crystal form. When it is, its color is thought due to trace amounts of phosphate or aluminium. The color in crystals is apparently photosensitive and subject to fading. The first crystals were found in a pegmatite found near Rumford, Maine, USA, but most crystals on the market come from Minas Gerais, Brazil. ...more on Wikipedia about "Rose quartz"
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