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Tourmaline is the most varicolored of all gemstones. It occurs in all colors, but red, green, and multicolored are its most famous gem colors. Scientifically, tourmaline is not a single mineral, but a group of minerals related in physical and chemical properties. The mineral elbaite is a member of the tourmaline group responsible for almost all the gem varieties. Three other members of the group -- dravite, schorl, and liddicoatite, are seldom used as gems. Dravite is brown in color, and is rarely transparent enough to be used as a gem. However, transparent stones, when found, are often cut as gems. They can be heat-treated to lighten their dark color. Schorl, which is dark gray to black, was once used in mourning jewelry, but does not have any gem use anymore. Liddicoatite is too rare to be used extensively, although its popularity as a gemstone is increasing.
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Although elbaite is a separate member of the tourmaline group, and occurs in all different colors, the term elbaite refers only to green tourmaline in the gem trade. The other color forms of elbaite have their own variety names on the gem market. Rubellite is the term used for red or pink tourmaline, and indicolite is the term used for blue tourmaline. A recent trend in the gem market is to call all tourmalines by the color designation as opposed to variety name, such that "rubellite" would be called "red tourmaline".
Rubellite, when exhibiting a deep red color, is the most valuable form of tourmaline. The pink, emerald-green and multicolored stones are also fairly expensive. Multicolored stones are truly a gemological wonder, as their beauty and uniqueness are unparalleled. An interesting form of multicolored tourmaline, adequately called watermelon tourmaline, has a red center surrounded by a green outer layer (or vice versa). When used as a gem, it is green on one side and red on the other.
Tourmaline exhibits the interesting electrical properties of pyroelectricity and piezoelectricity. When heated or rubbed, it attracts dust and dirt particles. This is caused by its atomic structure, which causes it to generate an electrical charge when heated or rubbed.
Heat Treatment can enhance the color of some tourmalines. Some greenish stones can be made deep green, some brownish-red stones can be made red, and some light pink stones can be made colorless through heating. The color of some light colored stones can also be made into a deeper hue, and dark, transparent dravite can be made lighter.
All colored tourmaline gems display pleochroism, meaning their color changes when viewed at different angles. In some gems, this effect is hardly noticeable, while in others it is strongly apparent. Gemstone cutters must take this into account when cutting a tourmaline, so the finished gem brings out its best color.
USES
Tourmalines of all colors are faceted into gems for jewelry, but the red, green, and multicolored stones are the most popular. Pink and green tourmalines from certain localities contain tiny, parallel inclusions, causing them to display a strong cat's eye effect when polished. Such stones are often cut as cabochons. Some pink, green, and multicolored tourmalines are also carved into ornamental figures and carvings.
SIMILAR GEMSTONES
Because of the limitless colors of tourmaline, it resembles numerous gemstones. The tourmaline will be divided into colors to list similar gemstones:
Green - emerald, peridot, hiddenite, demantoid, tsavorite, zircon
Red - ruby, spinel, garnet
Pink - rose quartz, kunzite, spinel, pink topaz, morganite, pink sapphire
Blue - aquamarine, blue topaz, sapphire, zircon
Purple - amethyst, spinel, purple sapphire
Brown - topaz, chrysoberyl, heliodor, citrine
Orange - topaz, chrysoberyl, heliodor, citrine, garnet, spinel, orange sapphire
Yellow - topaz, chrysoberyl, heliodor, citrine, garnet, spinel, orange sapphire
Colorless - rock crystal, diamond, white zircon, silver topaz, goshenite, colorless sapphire
Multicolored - The multicolored tourmalines are unique; there are no gems that resemble the multicolored tourmalines. Ametrine, a multicolored mixture of purple amethyst and orange-brown citrine, has characteristic colors that will not be confused with multicolored tourmalines.
