Tiger Iron

Tiger’s-eye is a variety of the mineral quartz in which the quartz has replaced crocidolite (a form of asbestos) without disturbing the original fibrous structure of the crocidolite; hexagonal (trigonal) crystal system; chemical composition SiO2
opaque
brown color with grey, silver band of hematite.

Identification

Optic Character: AGG, if not opaque; DR reaction possible in cat’s-eye Refractive Index: 1.544-1.553
Birefringence: .009 (often not detectable)
Pleochroism: none
Ultraviolet Fluorescence: inert
Absorption Spectra: not diagnostic
Cause of Color: generally iron oxide
Specific Gravity: 2.64 to 2.71
Polish Luster: vitreous
Fracture: splintery to conchoidal (in cat’s-eye)
Luster: vitreous to silky
Cleavage: none
Identifying Characteristics: fibrous structure (causes the chatoyancy); the wavy fibrous structure of tiger’s-eye and hawk’s-eye is usually distinctive.
Crystal Habit: massive
Hardness: 7
Toughness: good

Gem Reference Guide, Published by GIA. ISBN 0-87311-019-6

Gemstones of the World, Published by Sterling Publishing Co., Inc NY, ISBN 1-4027-4016-6

Encyclopedia of GEMSTONE, Published by ISHINSHA CO., LTD. ISBN 978-986-251-831-1