Ussingite

General Information:
 Chemical Formula:
Na2AlSi3O8(OH)
 Composition:
(Molecular Weight = 302.22 gm)
Sodium 15.21 % Na
Aluminum 8.93 % Al
Silicon 27.88 % Si
Hydrogen 0.33 % H 
Oxygen 47.65 % O 
 Empirical Formula:
Na2AlSi3O8(OH)
 Environment:
Pegmatites.
 Locality:
Kangerdluarusuk, Greenland.
Physical Properties:
 Cleavage:
[???] Good, [???] Good, [???] Good
 Color:
white, light violet red, dark violet red, pink, or reddish violet.
 Density:
2.46 - 2.5, Average = 2.48
 Diaphaniety:
Transparent
 Habits:
Massive - Uniformly indistinguishable crystals forming large masses., ,
 Hardness:
6.5 - Pyrite
 Luster:
Vitreous (Glassy)
 Streak:
white
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