Kyanite

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Kyanite

General Information

Kyanite is a polymorph with two other minerals: andalusite and sillimanite. A polymorph is a mineral that shares the same chemistry but a different crystal structure with other minerals. Kyanite is an attractive mineral that has a deep blue color in most specimens. Kyanite has a unique characteristic in that it has a wide variation in hardness. In the same crystal, the hardness of kyanite is about 4.5 when scratched parallel to the long axis of the crystal and approximately 6.5 when scratched perpendicular to or across the long axis. Other minerals have variable hardness on different crystal faces due to a different concentration and oreintation of the atoms in the structure. Diamond is one such mineral, a fact gem cutters take advantage of often

Chemistry: Al₂SiO₅, Aluminum Silicate	Class: Silicates	Subclass: Nesosilicates	Color: Blue; can be white, gray or green	Streak: White	Luster: Vitreous to almost pearly
Transparency: Transparent to translucent	Crystal System: Triclinic; bar 1	Hardness: 4.5-6.5	Cleavage: Good in direction parallel to the flat pinacoid face	Fracture: Splintery	Specific Gravity: 3.58+
Crystal Habits: Flat, pinacoid dominated, prismatic crystals often embedded in metamorphic rocks and quartz veins	Uses: Manufacture of spark plugs, etc. and as mineral specimens	Associated Minerals: Biotite, Staurolite, Garnets, Quartz, Andalusite, Sillimanite	Other Characteristics: Sometimes intergrown with staurolite	Notable Occurrences: Brazil; North Carolina and Georgia, USA; Switzerland; Russia; Serbia; India; Kenya	Best Field Indicators: Crystal habit, color, luster and unusual hardness

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