Specimen with eudral, sharp prismatic crystals of arfvedsonite up to 1,6 cm long on K Feldspar matrix. Color is black and display typical aligned striation on the prism crystal faces, parallel to the c-axis.
Formula :
Na3(Mg,Fe2+)4Fe3+[OH/Si4O_11_]2
System: monoclinic Hardness:5-6 Rarity:not common
Strunz id:VIII/F.8-90 -
SILICATES
Name origin: The arfvedsonite group minerals are sodium amphiboles defined with A(Na+K+2Ca)> 0.5 apfu and 0.5 apfu < C(Al+Fe3++2Ti) < 1.5 apfu with Fe as the dominant element in the C3+ position.
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 Specimen weight:38 gr.
 Crystal size:Up to 1,6 cm
 Overall size: 55mm x 35 mm x 27 mm
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