Macdonaldite

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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