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Gemstones 250x250

The Mineral afghanite

Translucent Bright Blue Afghanite

Afghanite is a rare and coveted mineral with a striking blue color, first identified in 1968. With a very close resemblance to Lazurite, and occurring together in the same deposits, Afghanite is distinguished by its unique crystal habit. Afghanite is named after its most significant locality in northern Afghanistan.

Chemical Formula

(Na,Ca,K)8Al6Si6O24(Cl2,SO4,CO3)3 · 0.5H2O

Color

Light to dark blue. Microcrystals from Italy may be be white, colorless, or light yellow.

Crystal System

Hexagonal

Properties

Streak
White
Hardness
5.5 - 6
Transparency
Translucent to Opaque
Specific Gravity
2.5 - 2.6
Luster
Vitreous
Cleavage
1, All
Fracture
Conchoidal to uneven
Tenacity
Brittle
Other ID Marks
Often fluorescent yellow to orange in longwave ultraviolet light.

Crystal Habits

In wide or elongated prismatic crystals with partial or stepped pyramidal terminations. Occasionally doubly terminated as bypyramidal crystals. Also as distorted crystal groups, as tabular microcrystals, grainy, and encrusting.

Additional Information

Composition
Hydrous silicate of sodium, calcium, and potassium, with chloride, carbonate, and sulfate radicals
In Group
Silicates; Tectosilicates; Feldspathoid Group
Striking Features
Color, crystal habit, and locality
Environment
In Lazurite veins in metamorphosed limestones.
Rock Type
Metamorphic

Uses

Afghanite is strictly used as a rare collectors mineral.

Noteworthy Localities

Afghanite is a rare mineral, with the only significantly important deposit being Sar-e Sang, Kokcha Valley, in Badakshan Province, Afghanistan, where it forms large and beautiful crystals that are almost always embedded on a white marble matrix. Small crusts of Afghanite occur in the vicinity of Slyudyanka, near the southern area of Lake Baikal, and white and colorless microcrystals in the vicinity of Vico Lake, near Viterbo, Italy.

Common Mineral Associations

Calcite, Lazurite, Pyrite, Diopside, Muscovite, Forsterite

Distingushing Similar Minerals

Lazurite - Forms in different crystals; has blue streak and poor cleavage.

afghanite Photos



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