Quartz (from the German quarz) is a large mineral group whose crystals are composed entirely of silica, found in abundance in the Earth’s crust. Totally colorless quartz is known as rock crystal, although most quartz occurs in different shades to which it owes its different names: citrine is yellow, amethyst is purple, and prasiolite is green. Others have simpler names, such as pink quartz or smoke quartz. All varieties of quartz can contain inclusions which alter their appearance and give them their special charm.
Examples include Venus-hair quartz, which contains golden-yellow needlelike rutile inclusions that resemble hair and flèches d’amour quartz (literally “love arrows”) with its needles of black tourmaline and iris quartz whose small internal flaws or fissures cause an iridescent effect. Sometimes inclusions can be present in such quantities as to render the quartz almost opaque.
This is the case with both jasper and pink quartz. Cartier often used the latter to make bases for decorative objects or sculpt small animal statues. Inclusions can also cause specific optical phenomena, such as spangled aventurine quartz or tiger’s eye quartz, so-called because of the slender, yellow crystalline needles it contains.
Translucent varieties of quartz include chalcedonies, the most precious of which is the chrysoprase whose bright green color is due to the presence of nickel. Silicon dioxide. Hardness: 7. Birthstone of natives to Taurus, Leo, Libra and Sagittarius. Pink quartz symbolizes tenderness while rutilated quartz symbolizes passion. Rare varieties of quartz are chrysoprase (Australia, Brazil, United States),“flèches d’amour” quartz (Brazil) and pink quartz (Brazil).