Citrine: Citrine is an attractive type of quartz, which is the commonest mineral on the earth's surface. But citrine itself is an uncommon macrocrystalline variety. Its yellow color brought about by its iron hydrate content, its reddish yellow from a trace of ferric iron. It forms hexagonal prisms, terminated by pyramidal shapes. Its faces are often striated, and the crystals twinned and distorted, having (read full)

Danburite: Danburite is a silicate of clear, prismatic crystals, with wedge-shaped terminations. It is occasionally pale yellow, a variety of gemstone feldspars group that resembles topaz. It is very hard, heavy, and has a transparent to vitreous to greasy luster. It fuses easily into a colorless glass, coloring the flame green, has a luminescence that is sky blue to pale blue-green, and also shows red therm (read full)

Dravite: Dravite also called Brown Tourmaline is a sodium magnesium-rich mineral in the Tourmaline group of silicates, with a hexagonal system. Other members of this group include elbaite (sodium lithium aluminum rich); schorl and buergerite (sodium iron rich); uvite (calcium magnesium rich); and liddicoatite (calcium lithium aluminum rich). A continuous solid solution series exists between uvite and dravi (read full)

Emerald: Emerald is the most prized variety of the mineral Beryl. It sometimes fetches higher prices than diamond. It appears as pale green to bright green. Though it is the green variety of beryl, not all gem-quality green beryls are called emeralds; yellow-green stones are called "heliodors;"soft blue-green or even pale green specimens are called "aquamarines." The typical color of emerald is a bea (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)

Kornerupine: Kornerupine is a rare magnesium aluminum borate silicate which occurs as transparent prismatic crystals of the orthorhombic system. It is hard and a has good cleavage in one direction. Colours include a characteristic dark green leaning to brown and a rare and attractive bright vanadium green. This pleochroic colours are brown to greenish brown. Chatoyant stones show a bright eye against a dark g (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)

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)

Tugtupite: Tugtupite is a mineral closely related to sodalite and hackmanite, all cyclosilicates whose structural silicate tetrahedrons are arranged in rings. It is also called beryllosodalite and reindeer stone, and crystallizes in the tetragonal system. It is found in fine-grained aggregates of crystals with its own distinctive cyclamen colour. Crystals are very small, tetragonal, almost cubic, or as shor (read full)

Kunzite: Kunzite is the pinkish lilac variety of the spodumene. These crystals or stones have a light pink hue because they constrain, traces manganese. Kunzite was first discovered in California in the early 20th century, and is known for its pleochroism. Its been noted that prolonged exposure to uv or solar lighting will diminish this stones color. This stone is generally sought after for its properties (read full)

Grandidierite: Grandidierite is a rare mineral that exhibits strong pleochroism, showing dark blue-green, colorless, or dark green depending on the viewing angle. It was first discovered in Madagascar and is one of the rarest gemstones in the world.With a hardness of 7.5 on the Mohs scale, grandidierite is suitable for jewelry but is rarely used due to its rarity. (read full)

Hiddenite: Hiddenite is the green variety of spodumene colored by chromium. Similar to kunzite (the pink variety of spodumene), hiddenite exhibits strong pleochroism and is valued for its distinctive green hue.With a hardness of 6.5 to 7 on the Mohs scale, hiddenite is suitable for jewelry but should be protected from sharp blows due to perfect cleavage. (read full)