Quartz (Molecule of the Month for March 1997)
If you gaze deep inside a crystal ball, you will see a versatile gemstone, one of the most popular gems on earth. Beautiful quartz, the "rock crystal" used in ancient times to make crystal balls and bowls, is today more often seen set in gold jewelry. Despite the popularity of quartz gems like amethyst, citrine, ametrine, rose quartz, onyx, agates, chrysoprase, rutilated quartz, and other quartz gemstone varieties, many people in the jewelry industry take quartz for granted because of its affordable price. Throughout history, quartz has been the common chameleon of gemstones, standing in for more expensive gemstones ranging from diamond to jade. But the incredible variety of quartz is now beginning to be appreciated for its own sake.
Purple to violet amethyst and yellow to orange citrine are jewelry staples that continue to increase in popularity. Ametrine combines the appeal of both amethyst and citrine as well as both the purple and yellow in one bicolored gemstone. Different colors and types of chalcedony, from agate to chrysoprase, have grown in popularity with the growing appreciation for carved gemstones and art cutting and carving. And unusual quartz specialties like drusy quartz, with its surface covered by tiny sparking crystals, and rutilated quartz, which has a landscape of shining gold needles inside, are adding variety and nature's artistry to unusual one-of-a-kind jewelry.
The pale pink color of quartz, 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, carvings, and architectural purposes.
Smoky quartz is a brown transparent quartz that is sometimes used for unusual faceted cuts. The commercial market is limited due to the limited demand for brown gemstones. This variety was sometimes known as smoky topaz in the past, which is incorrect and misleading, since the mineral variety is quartz, not topaz.
The transparent colorless variety of quartz is still known as rock crystal. Long ago, people believed that rock crystal was a compact form of ice: crystallos actually means "frozen." The best rock crystal has the clarity and shimmer of water. Although colorless quartz is relatively common, large flawless specimens are not, which is why crystal balls these days are made of glass, not quartz. Rock crystal has often been used in jewelry, particularly carved pieces. Many stunning Art Deco jewelry designs featured the black and white quartz combination of rock crystal and onyx. Colorless quartz crystals have also become popular in jewelry due to the popularity of legends about the powers of quartz crystals. Many people believe that wearing quartz crystals benefits a person's health and spiritual well being.
Rutilated quartz and tourmalinated quartz
While most varieties of transparent quartz are valued most when they lack inclusions, some 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. Less well known is a variety called tourmalinated quartz which, instead of golden rutile, has black or dark green tourmaline crystals.
Quartz that is formed not of one single crystal but finely grained microcrystals is known as chalcedony. The variety of chalcedony is even greater than transparent quartz varieties because it includes cryptocrystalline quartz with patterns as well as a wide range of solid colors. Agates are banded, bloodstone has red spots on a green ground, moss agate has a vegetal pattern. Jasper sometimes looks like a landscape painting. Another staple of the jewelry industry is black onyx, chalcedony quartz which owes its even black color to an ancient dying process that is still used today. Carnelian, another chalcedony valued in the ancient world, has a vivid brownish orange color and clear translucency that makes it popular for signet rings and seals. Chrysoprase, a bright apple green translucent chalcedony, is the most valued. It was a particular favorite of Frederick the great of Prussia, who loved its bright green color. It can be seen today decorating many buildings in beautiful Prague, including the Chapel of St Wencelas. Chrysoprase is found today mostly in Australia. Unlike most other green stones, which owe their color to chromium or vanadium, chrysoprase derives its color from nickel. Its bright even color and texture lends itself well to beads, cabochons, and carvings.
Formal Chemical Name (IUPAC)
Update by Karl Harrison
(Molecule of the Month for March 1997 )