If crocidolite has not been completely replaced by silica, the original grayish blue color of crocidolite remains and produces what is called hawk’s eye or falcon’s eye.
Chanthaburi ...
Glaucophane, crocidolite, riebeckite and arfvedsonite form a somewhat special group of alkali-amphiboles.
Enhancements
Crocidolite is not enhanced.
More information on gemstone enhancements.
Crocidolite (Hawk's Eye) ...
Tiger Opal (see Jasper) Tiger Eye - Mohs Hardness: 7- Treatment: None - Color: Shades of honey yellow and brown Formed from hawk's eye where the iron in inclusions of crocidolite has oxidized to a brown color, keeping the fibrous structure.
aka African Cat's-Eye, Cat's-Eye, Crocidolite, Tigerseye, Tiger's-Eye
Tigereye is a quartz with rich yellow and brown stripes, and a fine golden luster. When viewed from the opposite direction, the colors are reversed.
The Chinese Pietersite is a fibrous a magnesium-rich alkalic amphibole whilst the Namibian variety is mainly crocidolite.
As I move my stone in the sunlight, bands are illuminated as the crocidolite fibers come into a reflective orientation with my eyeball, when rotated into a non reflective orientation the bands become dark. This is the secret of the chatoyancy.
Heaney, published on the Geological Society of America website [3], the quartz crystal growth in tiger's-eye is synchronous with the crocidolite through a 'crack-seal vein-filling' process: "Our study has revealed that the textures responsible for ...
It seems that rather than chalcedony replacing crocidolite, this gem is actually a combination of crocidolite and layers of crystalline quartz (Science News, 4/26/2003).
Tiger's Eye also known as Crocidolite Cat's Eye or African Cat's Eye, is yellow or brown in color. The stones get a silk like luster when polished.
Overview: Tigereye is derived from a mineral called crocidolite, which has been oxidized to golden brown from it's original blue color and has been completely replaced by quartz. It is considered to be the most popular chatoyant gem.
Tiger's Eye is a type of microcrystalline chatoyant quartz that has replaced the asbestos mineral crocidolite to produce its unique appearance: Bands of a yellowish-brown to reddish-brown and when viewed from the opposite direction, ...
It is an opaque to translucent blue variety of quartz, owing its color to microscopic inclusions of fibrous magnesioriebeckite or crocidolite.
Hawk's eye is a green, grey or blue variety of quartz that has parallel, fibrous inclusions of crocidolite that give it a greenish cat's eye effect (chatoyancy). This mineral has a silky luster.
Tigereye is a yellowish brown cryptocrystalline quartz in which quartz has replaced crocidolite, a fibrous, asbestos-like mineral. The parallel fibrous structure produces a characteristic chatoyance (silky sheen), or even a cat's-eye effect.
This is coarse grained blue colored quartz, the inclusions of crocidolite fibres causes this color. Deposits found in Australia, Scandinavia, south Africa, and Virginia; can be confused for lapis lazuli.
Dendritic Agate ...
It occurs in a yellow and yellowish-brown material that pseudomorphous after crocidolite (blue asbestos). When cut cabochon with the base parallel to the fibers, it produces a cat's eye effect. Principal sources: South Africa.
Tiger's eye is a type of chatoyant quartz with fibrous inclusions (especially crocidolite). This stone is sometimes heat-treated. Tiger's eye has a hardness of 7.0.
Carnelian, agate, quartz cat's-eye, jasper (containing earthy impurities), and those materials in which quartz has more or less completely replaced other substances, such as silicified crocidolite, petrified wood, chrysocolla quartz, etc.
eye is usually highly polished and set as a cabochon (or cut as a bead) to display the stone's chatoyancy (light reflected in thin bands within the stone). Tiger's eye is a type of chatoyant quartz with fibrous inclusions (especially crocidolite).
12: Crocidolite
Sec. IV, Ch. 13: Euclase
Sec. IV, Ch. 14: Garnet, Carbuncle, & Cinnamon Stone
Sec. IV, Ch. 15: Hematite
Sec. IV, Ch. 16: Hiddenite
Sec. IV, Ch. 17: Iolite
Sec. IV, Ch. 18: Jade
Sec. IV, Ch.
 See also: Quartz, Stone, Color, Crystal, Mineral
  
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