Kyanite
Current inventory: 0 gem
 

  
Kyanite is named from the Greek word kyanos, meaning blue, the most common color of this mineral.

Discovered in 1789;   IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

Al₂SiO₅ 

Aluminum Silicate

Molecular Weight:

162.05 gm

Composition:

Aluminum

33.30 %

Al

62.92 %

Al₂O₃

Silicon

17.33 %

Si

37.08 %

SiO₂

Oxygen

49.37 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

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:

Polymorph of Andalusite and Sillimanite

Varieties:

Chrome-Kyanite

Synonyms:

Blue Talc, Cyanite, Distene, Disthene, ICSD 27771, PDF Nov-46, Rhaeticite

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:

Perfect on {100}, good on {010}, (100) ^ (010) = 79°; parting on {001}

Fracture:

Splintery

Tenacity:

Brittle

Moh's Hardness:

5.5 - 7.0 (varies with direction)

Density:

3.53 - 3.65 (g/cm³)

Luminescence:

Not Fluorescent

Radioactivity:

Not Radioavtive

Optical Properties

Color:

Blue, Green, Yellow, Orange, Pink, White, 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

Common Impurities:

Fe

Type Locality:

None (wide spread world wide occurrences)

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. A recent find in Tanzania has produced beautiful orange crystals. 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 chemical formula but have different crystal structures. Notable sources of gem material are Minas Gerais, Brazil, Nepal, Loliondo, Tanzania and Tibet.

Distribution: Widely distributed, even in good crystals. From Mt. Greiner, Zillertal, Tirol, Austria. At Alpe Sponda, Pizzo Forno, and at Alpe Campolungo, Tessin, Switzerland. In the Pfitschtal, Trentino-Alto Adige, Italy. From Röros, Norway. Around Yekaterinburg (Sverdlovsk), Ural Mountains, Russia. At Elovyi, Klavoloke, Karelia. From Sultan Hamud, Machakos district, Kenya. Large crystals from a number of localities in Minas Gerais, Brazil, as at Barro Prêto, São José do Jacuri. Beautiful orange crystals from Nani, Loliondo, Arusha Region, Tanzania. In the USA, at Lyme, Grafton County, New Hampshire; at Judd's Bridge, Litchfield County, Connecticut; at Darby, Delaware County, Pennsylvania; from near Bakersville, Mitchell County, and near Burnsville, Yancy County, North Carolina; on Willis Mountain, Buckingham County, Virginia.
 

  
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