Mineral - Afghanite
Afghanite
Chemical Properties
Mineral Class
Silicates
Toxicity
none
Formula
(Na,K)₂₂Ca₁₀(Si₂₄Al₂₄O₉₆)(SO₄)₆Cl₆
Unit Cell
a=12.77 c=21.35 Z=3
Physical Properties
Hardness
5.5 - 6
Streak
white
Density
Normal (2-3,5)
Cleavage
Perfekt after (10 1 0)
Fracture
conchoidal
Tenacity
Brittle
Optical Properties
Color
bluecolorless
Birefringence
0.006
Luster
Vitreous
Transparency
translucent,
transparent
Pleochroism
Geomineralogical Properties
Crystal System
trigonal
Point Group
ditrigonal-pyramidal - 3m
Space Group
P31c (159)
Habit
lath-shaped, prismatic, tabular
Formation
Formed by contact metasomatism in silicated limestones or marbles through the interaction with alkali-, chloride-, and sulfate-rich hydrothermal solutions
Paragenesis
Twinning
Rarity
Rather rare
Synonyms
Afghanite, Natrodavyne
Composition
Elements
Mass
SiO₂
30.80
Al₂O₃
25.00
CaO
16.50
Na₂O
12.60
K₂O
2.70
Cl
4.60
H₂O
0.70
CO₂
0.40
SO₃
8.50
Afghanistan (Bariand et al. 1968)
Groups and Members
Feldspathoid-Supergroup
Cancrinite-Group
Name and first record : Named after the type locality country. Discovered in Afghanistan in 1967.
Chemistry :
Synonyms :
Varieties :
Abbreviation : Afg
literature
Bariand, P., Cesbron, F., & Giraud, R. (1968). A new special mineral: the Afghanite de Sar-e-Sang, Badakhshan, Afghanistan. Comparison with les minéraux de groupe de la cancrinite. Bulletin de Minéralogie , 91 (1), 34-42.