mineral
Chiastolite
Andalusite variety Chiastolite
Hardness 7-7.5, color brown to gray with black cross, luster vitreous to dull, crystal structure orthorhombic, cleavage good, specific gravity 3.13-3.17
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Physical properties
Hardness 7-7.5, color brown to gray with black cross, luster vitreous to dull, crystal structure orthorhombic, cleavage good, specific gravity 3.13-3.17
Formation & geological history
Forms in contact metamorphic rocks, such as hornfels, when aluminum-rich argillaceous rocks are heated by igneous intrusions. The dark cross pattern is caused by carbonaceous inclusions pushed to the crystal edges during growth.
Uses & applications
Primarily used as a lapidary material for jewelry (cabochons, pendants) and as a collector's specimen.
Geological facts
The distinctive cross pattern is known as a "macle" and has historical and religious significance, often used as an amulet.
Field identification & locations
Easily identified by its characteristic dark cross pattern on a lighter background. Found in locations such as Spain, Australia, China, and the USA.
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