Images
Formula: (Na,K)22Ca10(Si24Al24)O96(SO4)6Cl6
Valence: (Na,K)22Ca10(Si24Al24)O96(S6+O4)6Cl6
Tectosilicate (framework silicate), cancrinite group of the
feldspathoid group
Crystal system: Trigonal
Specific gravity: 2.55 measured, 2.65 calculated
Hardness: 5½ to 6
Streak: White
Colour: White, light blue, dark blue
Environments
Minerals associated with afghanite include lazurite,
sodalite, nepheline,
phlogopite, olivine,
diopside, vesuvianite,
calcite and pyrite
(HOM).
Localities
At the type locality, Ladjuar Medam, Sar-e-Sang, Kuran wa Munjan District, Badakhshan, Afghanistan, a specimen
has been found that contains well formed thin tabular crystals of afghanite that cut through
lazurite in several directions; the laths do not extend beyond the
lazurite grains. Common associated minerals are
phlogopite, diopside and
oligoclase
(CM 17.1.47-52).
Other associated minerals include calcite,
olivine, nepheline,
pyrite, sodalite and
vesuvianite
(Mindat).
Afghanite also forms pseudomorphs after
quartz
(Dana).
Afghanite from Ladjuar Medam -
Image
At Kimmirut, Baffin Island, Qikiqtaaluk Region, Nunavut, Canada, afghanite appears as rounded isolated
grains in small amounts in nepheline, associated with
diopside and lazurite
(CM 17.1.47-52).
At Case Collina, Pitigliano, Grosseto Province, Tuscany, Italy, afghanite occurs in silicified
limestone xenoliths in
pumice
(HOM).
Afghanite from Case Collina -
Image
At Malo-Bystrinskoe lazurite deposit, Malaya Bystraya River Valley, Slyudyansky District, Irkutsk Oblast, Russia,
afghanite occurs in very minor amounts. Tabular afghanite was identified in a
diopside - phlogopite -
lazurite - calcite rock
(CM 17.1.47-52).
Afghanite from Malo-Bystrinskoe -
Image
At Lyadzhvardara deposit, Badom-Dara, Shakhdara range, Roshtqal'a, Gorno-Badakhshan, Tajikistan, a specimen has
been found that contains approximately 13% by volume of afghanite. Crystals are stout to slender tabular; in
some clusters, they are present almost to the exclusion of lazurite.
Afghanite and lazurite-afghanite clusters are
surrounded by diopside
(CM 17.1.47-52).
At Edwards Mine, Edwards, St. Lawrence County, New York, USA, a
lapis-lazuli specimen was collected from the
sphalerite orebody. Major minerals are
pargasite, diopside,
oligoclase and lazurite.
Afghanite amounts to about 1% by volume. It occurs as rounded grains that lack crystal outline and are
commonly separated from lazurite. A few grains of tabular
afghanite are also present in the thin section
(CM 17.1.47-52).
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