Quartz
Quartz group
Color: clear, pink, blue, smoky brown/black, orange, grey, rose, purple, yellow, green
Moh's hardness: 7
This group of gemstones is named after a Slavic word for "hard", and includes a number of minerals with the same chemical composition. Due to its versatility and affordable price, quartz is one of the most favored gems throughout history. Some of the most popular quartz gems are: amethyst, citrine, ametrine, rose quartz, onyx, agate, rutilated quartz, carnelian, chalcedony and tiger's eye.
Purple to violet amethyst and yellow to orange citrine are often seen in fashion and fine jewelry. Ametrine combines the appeal of amethyst's purple and citrine's yellow in one bi-colored gemstone. Different colors of chalcedony are common in carved gemstones. While transparent quartz varieties are valued most when they lack inclusions, other varieties are valued chiefly because of inclusions. The most popular of these is known as rutilated quartz. Rutilated quartz is transparent rock crystal with golden needles of rutile arrayed in patterns inside. Every pattern is different and some are breathtakingly beautiful. The inclusions are sometimes called Venus hair.
Quartz with a pale pink color, which can range from transparent to translucent, is known as rose quartz. The color is a very pale and delicate powder pink. Transparent rose quartz is very rare and is usually so pale that it does not show very much color except in large sizes. The translucent quality of rose quartz is much more available and is used for beads, cabochons and carvings.
Smoky quartz is a brown transparent quartz. This variety was sometimes referred to as smoky topaz in the past, which is incorrect and misleading since the mineral variety is quartz, not topaz.
Tiger's eye quartz contains brown iron, which produces its golden-yellow color. Cabochon cut stones of this variety show the chatoyancy (small ray of light on the surface) that resembles the eye of a tiger. The most important deposit of tiger's eye is in South Africa, though it is also found in Western Australia, Myanmar (Burma), India and the United states.