set of various tiger-eye natural mineral stones and gemstones (tigers eye, bull-eye, hawk-eye)
Set of various tiger-eye natural mineral stones and gemstones (tigers eye, bull-eye, hawk-eye). Copyright : vvoennyy


Tiger's eye is a chatoyant gemstone that is usually a metamorphic rock with a golden to red-brown colour and a silky lustre. Tiger's Eye, a popular yet inexpensive gemstone, is a pseudomorph of compact Quartz after the fibrous mineral Crocidolite. It is formed when the Quartz takes over and dissolves the Crocodolite, leaving the Quartz in a finely fibrous and chatoyant form.

As members of the quartz group, tiger's eye and the related blue-coloured mineral hawk's eye gain their silky, lustrous appearance from the parallel intergrowth of quartz crystals and altered amphibole fibres that have mostly turned into limonite.

Tiger's Eye forms when Quartz forms over existing bluish-gray Crocidolite, and eventually entirely replace it. Crocidolite is a type of asbestos mineral, which means its composition is of fine, dense fibers. These fibers form in a parallel yet wavy orientation, and this causes the intriguing chatoyant effect exhibited in Tiger's Eye. During the replacement process, the iron within the Crocidolite dissolves and stains the Quartz, thereby providing the golden yellow to brown color of the Tiger's Eye.



When cutting and polishing Tiger's Eye gemstones, skillful orientation to the fibrous structure must be applied to achieve the best chatoyancy. Ideally the cut should be perfectly parallel to the length of the fibers to achieve fullest chatoyancy. Cat's eye effect in Tiger's Eye do exist, but are uncommon in perfect form due to the wavy nature of the fibers.

Other forms of tiger's eye

Tiger iron is an altered rock composed chiefly of tiger's eye, red jasper and black hematite. The undulating, contrasting bands of colour and lustre make for an attractive motif and it is mainly used for jewellery-making and ornamentation. Tiger iron is a popular ornamental material used in a variety of applications, from beads to knife hilts.

Hawk's Eye Bluish-gray variant of Tiger's Eye, lacking the yellow or brown color. Hawk's Eye is formed from an incomplete pseudomorphism of Quartz after Crocidolite.

Serpentine deposits in which are occasionally found chatoyant bands of chrysotile fibres have been found in the US states of Arizona and California. These have been cut and sold as "Arizona tiger-eye" and "California tiger's eye" gemstones.

 
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