The Citrine GroupCitrine

Colour: Light yellow to dark yellow, gold-brown

Color of streak: White

Mohs' hardness: 7

Density: 2.65

Cleavage: None

Fracture: Conchoidal, very brittle

Crystal system: Hexagonal (trigonal); hexagonal prisms with pyramids

Chemical composition: SiO2 silicon dioxide

Transparency: Transparent

Refractive index: 1.544-1.553

Double refraction: +0.009

Dispersion: 0.013 (0.008)

Pleochroism: Natural: weak; yellow-light yellow Heat-treated: none

Absorption spectrum: Not diagnostic

Fluorescence: None

The name is derived from its lemon yellow color. The coloring agent is iron. Natural citrines are rare. Most commercial citrines are heat-treated amethysts or smoky quartzes. Brazilian amethyst turns light yellow at 878 degrees F (470 degrees C) and dark yellow to red-brown at 1022-1040 degrees F (550-560 degrees C). Some smoky quartzes turn into citrine color already at about 390 degrees F (200 degrees C). Almost all heat-treated citrines have a reddish tint. The natural citrines are mostly pale yellow. Names for citrine such as Bahia, Madeira, or Rio Grande topaz are improper and no longer accepted in the trade as they are deceptive. On the other hand, when one, for example, speaks of Madeira color and/or Madeira citrine, this is a correct usage; the expert properly connects a certain color with the locality name. Deposits of natural-colored citrines are found in Brazil, Madagascar, and the United States, as well as in Argentina, Burma (Myanmar), Namibia, Russia, Scotland, and Spain. Well-colored citrines are used as ring stones and pendants; less attractive stones are made into necklaces or ornaments. Can be confused with many yellow gemstones, especially apatite, golden beryl, orthoclase, topaz, and tourmaline, as well as tinted glass. Prasiolite Colour: Leek-green Color of streak: White Mohs' hardness: 7 Density: 2.65 Cleavage: None Fracture: Conchoidal, very brittle Crystal system: Hexagonal (trigonal); hexagonal prisms Chemical composition: SiO2 silicon dioxide Quartz Species Transparency: Transparent Refractive index: 1.544-1.553 Double refraction: +0.009 Dispersion: 0.013 (0.008) Pleochroism: Very weak; light green, pale green Absorption spectrum: Not diagnostic Fluorescence: None Prasiolite (Greek—leek-green stone) is not found in nature. It is produced by heating violet amethyst or yellowish quartz from the deposit Montezuma in Minas Gerais, Brazil, to a temperature of about 930 degrees F (500 degrees C). Other deposits of heatable amethyst have recently been reported in Arizona. In sunlight, the color commonly fades. Can be confused with precious beryl, peridot, tourmaline, and other green gemstones. 1 Citrine, heat-treated, rough 2 Citrine, heat-treated, faceted 3 Citrine, heat-treated, rectangle 4 Citrine, natural, rough 120 5 Citrine, natural, oval 6 Citrine, 2 emerald cuts 7 Prasiolite, rough 8 Prasiolite, 2 faceted stones