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Download hereGENERAL DESCRIPTION
Afghanite is a complex hydrated sodium aluminosilicate of calcium and potassium, containing also carbonates, sulphate and chlorine ions. Afghanite forms within skarns (limestones having undergone a contact metamorphism due to cooling granites), in the veins containing lazurite or volcanic tuffs. Afghanite is regularly associated to pyroxenes and zeolites in addition to lazurite, sodalite, pyrite and some carbonates.
Afghanite is blue, its crystals are tabular, sometimes pyramidal or in irregular grains.
There exists a few localities where afghanite is found: Sar-e-Sang in Afghanistan ; Pitigliano, Vetralla, Bassano, Sacrofano and the Monte Somma in Italy; Ettringen in Germany and the Tunka valley in Russia.
Yet, there is no deposit known in France.
Originating from Sar-e-Sang, the types are kept at the Muséum national d’Histoire naturelle in Paris. This type was offered by the "Sorbonne Collection" of mineralogy in 1967. The second type is kept at the National History Museum of London.
Did you know? Italians are expert with minerals related to afghanite. Accordingly, a rather important number of those minerals were found in the Latium and Vesuvio volcanism. Another (relatively similar) outcrop is known in Germnay (Eifel volcanism). So why still nothing in France’s Massif Central, Europe’s largest volcanic field ?
HISTORY : Named after its type-locality : Afghanistan
Species described in 1968 by Pierre Bariand, Fabien Cesbron & Roger Giraud, French mineralogists
Type-locality: Mine de Lapis-lazuli, Sar-e-Sang, Province de Badakshan, Afghanistan
CHEMICAL FORMULA : (Na,Ca,K)8 (Cl2, SO4, CO3) (Al6 Si6 O24) 0,5H2O
CRYSTAL SYSTEM : Hexagonal
COLOR : Blue
DIAPHANIETY : Transparent
LUSTER : Vitreous
STREAK : White
MORPHOLOGIE : Tabular crystals
HARDNESS : 5,5-6,0
CHEMICAL CLASS: 2,65
DENSITY : VIII - Silicates
GROUP : Gmelinite-offretite
STRUNZ CLASS BEFORE 2001 : 8/J.09-50
STRUNZ CLASS AFTER 2001 : 9.GG.05
