Amethyst: Amethyst is the most coveted stone in the quartz group, and it is sometimes confused with beryl. It is usually found layered with milky quartz, and its color varies from purple to violet. It is sometimes sold as Ametrine, but this is actually a combined variation of 2 gems; Amethyst and Citrine. Amethyst like Agate Chalcedony can be found in geodes. There are many types of synthetic Amethyst aro (read full)

Apatite: Apatite is a gemstone that appears similar to tourmaline in its blue green form. It comes in yellow, green, pink, purple, violet, clear, and cat's eye. The most popular and valuable versions of Apatite are currently the blues that look like tourmaline. In fact its Greek name means "cheat" because it's often passed for other more valuable gems. Apatite streaks white to white yellow. The light gre (read full)

Spinel: Spinel is an extensive group of minerals in which magnesium may be replaced with iron, zinc, and above all, manganese. The hardness and fine colors of gem quality spinel, known as Noble Spinel, set it apart as a gem material from other types of spinel. It normally occurs as distinct octahedral crystals, as clusters also of octahedral habit, or as characteristic twins. The crystals are often iso (read full)

Ruby: Ruby is the most valuable variety of Corundum. The color varies from fiery vermilion to violet red, but because rubies are pleochroic, different colors are also found in the same stone; bright or sometimes brick red in one direction, tending to carmine in the other. The color is also accompanied by marked fluorescence which is stimulated by ordinary, artificial light, and above all, by the ultra (read full)

Iolite: Iolite is the violet-colored variety of Cordierite (named after French geologist P. Cordier), a silicate of aluminum and magnesium, with an orthorhombic crystal system. Though the name cordierite is used by mineralogists, the name iolite has become established among gemologists. It appears as stubby, prismatic crystals, pesudo-hexagonal twins with a glassy appearance. It is frequently microgranul (read full)

Rubellite Tourmaline: Rubellite is the pink to red variety of Tourmaline, which is a complex borosilicate of aluminum and alkali, with iron, magnesium, and other cations. It is found as fine acicular crystals in rocks, or as large individual crystals grown upon matrix where they may reach a weight of several kilograms. Most form elongated and striated trigonal (three-sided) prisms and these are terminated with trigona (read full)

Scapolite: Scapolite is a mixed crystal series, a complicated sodium calcium aluminum silicate group composed of calcium-rich meionite, and sodium-rich marialite. It appears as yellow, blue, pink, violet, or colorless prismatic crystals with a tetragonal system, mostly surface-growing, with perfect cleavage. These crystals are usually in aggregates that are massive granular, long columnar, dense, with vitr (read full)

Lapis Lazuli: Lapis lazuli is composed of several minerals in small quantities - augite, calcite, diopside, mica, hauynite, hornblende, pyrite. Because of this some experts consider it a rock, more than a mineral. The main ingredient of Lapis lazuli is Lazurite. It has a uniform, massive, or sometimes granular appearance, with fairly distinct crystals. It is semi-opaque to opaque, with a surface that can take (read full)

Dumortierite: Dumortierite is a variety of gemstone of basic aluminum borosilicate with an orthorhombic crystal system. It appears usually in columnar or fibrous, radiating aggregates, sometimes reddish brown, dark blue, violet-blue. On the rare occasions that dumortierite forms crystals, they are prismatic. Faceted or prismatic blue or violet samples are rare, due to scarcity of individual crystals. It is (read full)

Zoisite: Zoisite is a hydrous calcium aluminum silicate in the Epidote group, with an orthorhombic crystal system, three crystal axes at right angles to each other, all of varying lengths. It appears in elongated, prismatic crystals, with fine parallel lines on the prism faces and usually poorly terminated. It also appears frequently in formless grains, poorly-defined crystals, rodlike aggregates and gran (read full)

Spodumene: Spodumene is a lithium aluminum silicate that crystallizes in the monoclinic system. It is one of several rock-forming minerals in the Pyroxene group, which are physically-related as their chemical content is quite similar and forms a chain. Fellow pyroxenes are jadeite, enstatite, diopside, hypersthene, augite, acmite, hedenbergite, pigeonite, and aegirineaugite. It appears as prismatic crystals (read full)

Sapphire: Sapphire is the blue variety of Corundum. Sapphires can be a very dark blue, to the point of seeming dense and blackish from a distance, sometimes accompanied by a blue to dull green pleochroism, which is only visible from the side in cut stones. They may also be a strong, but not too bright blue, easily recognizable from a distance, this being the real color. Other possibilities are light, usual (read full)

Axinite: Axinite is a honey brownish to dark brown gem that is named after the axe head like crystal structures that are usually found. It is usually found in and around granite deposits, and is often mistaken (and sometimes sold by mistake) as smokey quartz. The gem is piezoelectric and because of this has been used to remove hair and lint from unwanted objects. A negative side effect of this is that it (read full)

Indicolite: Indicolite is the blue sodium-rich variety of Tourmaline, and may come in all shades of blue, from light-blue, violet-blue to deep red or deep green. It generally appears quite a deep blue, even the color of dark blue ink, perhaps appearing green in one direction because of its strong pleochroism. Sometimes indicolite is an overall greenish blue, which, unlike the color of greenish blue sapphire, (read full)

Labradorite: Labradorite is a sodium-rich plagioclase feldspar which displays a particular type of iridescence on a dark ground. Plagioclase feldspars are rock-forming, calcium-sodium minerals which form a continuous series ranging from albite, through oligoclase, andesine, labradorite, and bytownite to anorthite. Precise classification is generally not possible in hand specimens, and their physical properties (read full)

Fluorite: Fluorite is a widely-distributed mineral in the Halide classification, and is now mined in vast quantities. It is a suitable mineral for collectors and is rarely cut as a gem, but massive varieties are carved as ornamental objects. It appears in cubes, octahedrons, dodecahedrons, while other forms are rarer. Compact, banded, and concretionary masses are frequently found. Most fine crystals of flu (read full)

Smithsonite: Smithsonite is a mineral in the group of Nitrates, Carbonates, Borates, with a hexagonal crystal system. It appears uncommonly in rhombohedral or scalenohedral crystals. But most of the time it appears with curved faces, like a thick creamy aqua-green mixture poured on rock and left to aggregate in clusters shaped like bunches of grapes, rounded, kidney-like, or to form like elegant icicles, and (read full)

Pyrope: Pyrope is the iron magnesium and aluminum silicate of the pyrope-almandine series in the Pyralspite group of the Garnet family. Its beautiful deep-red gem quality makes it one of the most popular. Pure pyrope is colorless, but its red color, sometimes very bright, is due to small quantities of chrome in the crystal structure. It appears as dodecahedral or trapezohedral crystals, dark red, usually (read full)

Watermelon Tourmaline: Watermelon Tourmaline is a bi-colored/tri-colored/parti-colored occurrence of Tourmaline, and this appearance is usually a feature of the variety known as Elbaite. When cut parallel to its base, this tourmaline exhibits a rose-red center, a very thin colorless band parallel to the surface of the crystal, and a brown or green outer layer. In parti-colored tourmaline the core is nearly colorless an (read full)

Taaffeite: Taaffeite is a very rare beryllium magnesium aluminum mineral. No other mineral has both beryllium and magnesium in its composition. It is one of the few gems to be discovered as a faceted stone instead of a rough, as most gemstones are. Rarely cut as a gem, taaffeite looks like a mauve-colored spinel, and its absorption spectrum is similar to it. But gemologists know they've found taaffeite when (read full)

Sillimanite: Sillimanite is a grayish-blue aluminum silicate with an orthorhombic crystal system. It is trimorphic with andalusite and kyanite. All three have the same chemical compound but their atoms each arrange to create three different crystal forms. It appears as long, slender crystals without distinct terminations, in off-white, gray, brown, pale green, slate-blue, blue-green, and these crystals are of (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)

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)

Diamond: In fact Diamond is the only gem material comprised of a single chemical element: pure carbon, like graphite. But the atoms in diamond have been forced into a compact, three-dimensional structure by the high pressures in the upper mantle, where it is formed. Thus diamond is much harder and has a higher specific gravity (3.52) than graphite . There is nothing comparable to it in hardness; it is ther (read full)

Rock Crystal (Quartz): Rock Crystal is the purest water-clear and colorless from of Quartz. It is known as mountain crystal (Bergkristall). It is the presence of impurities that gives other varieties of quartz their colors. It is found in beautifully formed crystals, often with complex terminations. These are usully bounded by the faces of six-sided prisms, which are almost always striated horizontally. Very often they (read full)

Coral: Corals are the supporting framework of small polyps. Each coral polyp, a tiny marine animal that lives in enormous colonies, extracts calcium carbonate from the sea and exudes it through their bases to build a protective home around and above itself. Each generation of polyps dies in its protective home and each succeeding generation builds on top of its predecessor. They precipitate calcareous m (read full)

Topaz: The transparent, colored crystals, which also have good luster, are widely used as gems.
Topaz is a silicate of aluminum containing fluorine and hydroxyl which occurs in a variety of delicate colors, nicely added by impurities. It is often found in short to long crystal prisms with pyramid-shaped ends, or just clean finished edges. It is often white, semiopaque, milky, or a faded yellow, (read full)

Zircon: Zircon is a zirconium silicate with a tetragonal crystal system, and also contains thorium and uranium. It appears as stubby, prismatic, isolated or sometimes dipyramidal, like two pyramids connected at their bases; or in twins, colorless to yellow, red, brown, gray or green, in irregular granules. It is very hard, heavy, with indistinct cleavage, and shell-like fracture. It is sometimes perfect (read full)