General Information:
Chemical Formula:
BaCa4[Si16O36(OH)2]·10(H2O)
Composition:
(Molecular Weight = 1,537.15 gm)
Barium 8.93 % Ba
Calcium 10.43 % Ca
Silicon 29.23 % Si
Hydrogen 1.44 % H
Oxygen 49.96 % O
Empirical Formula:
BaCa4Si16O36(OH)2·10(H2O)
Environment:
Sanbornite-bearing metamorphic rocks near a granodiorite contact.
IMA Status:
Approved IMA 1965
Locality:
Big Creek - Rush Creek sanbornite deposit, 5 miles NE of Trimmer, Fresno Co., California.
Name Origin:
Named for Grodon Andrew Macdonald (1911-1978), American volcanologist, University of Hawaii.
Physical Properties:
Cleavage:
[010] Perfect, [001] Good, [100] Indistinct
Color:
colorless or white.
Density:
2.27
Diaphaniety:
Transparent
Habits:
Acicular - Occurs as needle-like crystals., ,
Hardness:
3.5-4 - Copper Penny-Flourite
Luster:
Vitreous - Silky
Streak:
white
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