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Kyanite
Current inventory:  0 gems
 

Chemistry:  Al₂SiO₅  [Aluminum Silicate]

Discovered in 1789;   IMA status: Valid (pre-IMA; Grandfathered).
Kyanite gets its name is from the Greek word kyanos, meaning blue, the most common color of this mineral.

Classification

Mineral Classification:

Silicates

Strunz 8th Ed. ID:

8/B.02-40

Nickel-Strunz 10th Ed. ID:

9.AF.15

9 : SILICATES (Germanates)
A : Nesosilicates
F : Nesosilicates with additional anions; cations in [4], [5] and/or only [6] coordination

Related to:

Sillimanite Group, Disthene Series, Dimorph of Andalusite and Sillimanite

Crystal Data

Crystallography:

Triclinic - Pinacoidal

Crystal Habit:

Crystals bladed and tabular, elongated, to 0.5 m; typically bent or twisted.

Twinning:

Lamellar common.

Physical Properties

Cleavage:

[100] Perfect, [010] Imperfect

Fracture:

Splintery, Parting on [001]

Tenacity:

Brittle

Hardness (Mohs):

5.5 - 7.0 (varies with direction)

Density:

3.53 - 3.65 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioavtive

Optical Properties

Color:

Blue, White, Green, Yellow, Pink, Black; can be zoned

Transparency:

Transparent, Translucent

Luster:

Vitreous, Pearly

Refractive Index:

1.712 - 1.734  Biaxial ( - )

Birefringence:

0.0150 - 0.0160

Dispersion:

Weak; r > v; 0.020

Pleochroism:

Weak; X = colorless, Y = violet-blue, Z = cobalt blue

Occurances

Geological Setting:

In gneisses, schists, included pegmatites, and quartz veins, from moderately high-pressure regional metamorphism of principally pelitic rocks; detrital in sedimentary rocks.

Common Associations:

Andalusite, Corundum, Gedrite, Hornblende, Mullite, Sillimanite, Staurolite, Talc

Type Locality:

n/a

Year Discovered:

1789

View mineral photos:

Kyanite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Kyanite is a beautiful gem that varies in color from pale blue to very dark blue to green and rarely yellow or pink. Crystals from Brazil may have both blue and green zoned lengthwise. The blue variety is most common and may have a beautiful sapphire-blue color. Kyanite is somewhat rare as a faceted gem due to its perfect clevage and extreme variability in hardness in different directions. Kyanite is trimorphous with Andalusite and Sillimanite meaning all three share the same basic chemistry formula but have different crystal structures. Notable sources of gem material are Minas Gerais, Brazil, Nepal and Tibet.
 

  
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