/ Mineral & Gemstone Database


Obsidian: Obsidian is an extrusive igneous rock, a volcanic glass formed by rapid cooling. Its essential component is glass. Its accessory components are magnetite, ilmenite, oxides and other minerals, such as feldspar. It has the same composition as dacite or rhyolite, with less than 1 percent water. Its color is shiny black, with clear conchoidal (shell-like)fracture, its texture glassy with rare micr (read full)


Oligoclase: Oligoclase is a mineral of the plagioclase feldspar series, other members of which are Labradorite and Anorthite. It forms as tabular crystals, which are commonly twinned, with parallel or criss-cross twinning striations. It appears as massive, granular, or compact. It may show brilliant reflections from inclusions. It is light, transparent to translucent, with a vitreous luster and may come in (read full)


Onyx: Onyx is a translucent to semitransparent variety of Agate, which in turn is a variety of Chalcedony or cryptocrystalline quartz that is porous and consists of straight or parallel banded agate of alternating shades of milky white and black, gray and black, black and red, white and red, white and brown. The term onyx has been erroneously applied as a suffix to Brazilian onyx, Mexican onyx, Orient (read full)


Opal: Opal is hydrated silicon dioxide. It has the same chemical composition as quartz but contains about one-tenth (and sometimes as much as one-third) water. It is never crystalline, but it displays a rich play of colors, or "fire" caused by the internal refraction of light by the array of tiny spheres of amorphous silica which for a compact, three-dimensional network in the mineral. It may be somew (read full)


Orthoclase: Orthoclase mineral is a silicate of potassium and aluminum, belonging to the Feldspar group. It has the same composition as microcline, but is stable at slightly higher temperatures. It occurs as prismatic, sometimes flat-sided crystals, but in rocks it is usually anhedral. It may be perfectly transparent and yellow or almost colorless, but it is more often semi-opaque and white to grayish-white, (read full)


Padparadscha: Padparadschah is the name given to the orange-yellow sapphire, a gem variety of Corundum. It is also differentiated from the yellow sapphire, and is one of the rarest varieties of corundum. The main sapphire-bearing rocks are marble, basalt, or pegmatite. It is mined mainly from alluvial deposits or deposits formed by weathering, rarely from the primary rock. It usually occurs in placer deposit (read full)


Pearl: Pearl is one of four main ornamental materials that are classified as "organic" gems, the other three being coral, ivory, and amber. About 92 percent of pearl is calcium carbonate, in the form of aragonite crystals, held together by an organic substance (concholin), which is identical to the horny outer layer of oyster shells, plus a small quantity of water. Mother-of-pearl has a simila (read full)