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Afghanite

Discovered in 1968;   IMA status: Valid (IMA approved 1968)

Chemistry

Chemical Formula:

(Na,Ca,K)₈(Si,Al)₁₂O₂₄(SO₄,Cl,CO₃)₃ · H₂O

Hydrated Sodium Calcium Potassium Aluminum Silicate Carbonate

Molecular Weight:

1,200.45 gm

Composition:

Potassium

2.28 %

K

2.75 %

K₂O

Sodium

9.19 %

Na

12.39 %

Na₂O

Calcium

11.69 %

Ca

16.35 %

CaO

Aluminum

13.26 %

Al

25.06 %

Al₂O₃

Silicon

14.27 %

Si

30.53 %

SiO₂

Hydrogen

0.08 %

H

0.75 %

H₂O

Carbon

0.10 %

C

0.37 %

CO₂

Sulfur

3.39 %

S

8.47 %

SO₃

Chlorine

4.58 %

Cl

4.58 %

Cl

— %

Cl

—1.03 %

—O=Cl₂

Oxygen

41.16 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/J.09-50

Nickel-Strunz 10th Ed. ID:

9.FB.05

9 : SILICATES (Germanates)
F : Tektosilicates without zeolitic H₂O
B : Tektosilicates with additional anions

Related to:

Cancrinite Group

Members of Group:

Cancrinite Group: Afghanite, Allorite, Biachellaite, Bystrite, Cancrinite, Cancrisilite, Davyne, Depmeierite, Franzinite, Giuseppetite, Hydroxycancrinite, Kircherite, Kyanoxalite, Liottite, Marinellite, Microsommite, Pitiglianoite, Quadridavyne, Sacrofanite, Tounkite, Vishnevite

Varieties:

None

Synonyms:

IMA1967-041

Crystal Data

Crystallography:

Hexagonal

Crystal Habit:

As stout to slender, thin tabular laths and as rounded grains or as massive - uniformly indistinguishable crystals forming large masses.

Twinning:

None

Physical Properties

Cleavage:

Perfect on [1010]

Fracture:

Conchoidal

Tenacity:

Brittle

Moh's Hardness:

5.5 - 6.0

Density:

2.55 - 2.65 (g/cm³)

Luminescence:

None

Radioactivity:

Barely Detectable; GRapi = 32.54 (Gamma Ray American Petroleum Institute Units)

Optical Properties

Color:

Light Blue to Dark Blue, Colorless

Transparency:

Transparent

Luster:

Vitreous

Refractive Index:

1.523 - 1.529  Uniaxial ( + )

Birefringence:

0.006

Dispersion:

n/a

Pleochroism:

None

Occurances

Geological Setting:

In thin veinlets cutting lazurite crystals (Sar-e-Sang, Afghanistan); in silicifed limestone xenoliths in pumice (Pitigliano quarry, Italy).

Common Associations:

Lazurite, Sodalite, Nepheline, Phlogopite, Olivine, Diopside, Vesuvianite, Calcite, Pyrite.

Common Impurities:

None

Type Locality:

Lapis-lazuli Mine, Sar-e-Sang, Badakhshan (Badakshan; Badahsan) Province, Afghanistan

Year Discovered:

1968

View mineral photos:

Afghanite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Afghanite is is a rare Feldspathoid mineral of the Cancrinite Group of minerals and is found in only a few locations worldwide. It is usually found associated with Lazurite and Sodalite. Crystals are blue to dark blue and usually moderately to heavily included. Gems are typically small and included but beautiful shades of saturated blue. Afghanite was discovered in 1968 in the Lapis-lazuli Mine, Sar-e-Sang, Badakhshan Province, Afghanistan and takes its name from that country.

Afghanite is named after the country of its discovery. It was discovered at the Lapis-lazuli Mine, Sar-e-Sang, Badakhshan Province, Afghanistan.

Locations for Afghanite: at Sar-e-Sang, Badakhshan Province, Afghanistan. In Russia, in the Malaya Bystraya and Tultuy lazurite deposits, near Lake Baikal, and in other unspecified deposits in eastern Siberia. From Lyadzhuar-Darinsk, Pamir Mountains, Tajikistan. In Italy, at the Pitigliano quarry, near Grosseto, Tuscany; on Monte Somma, Campania; from Vetralla and Bassano, Latium. In the Edwards mine, Edwards, St. Lawrence County, New York, USA. At Lake Harbour, Bafin Island, Newfoundland, Canada.

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