Macdonaldite

General Information: Chemical Formula:BaCa4[Si16O36(OH)2]·10(H2O) Composition:(Molecular Weight = 1,537.15 gm)Barium 8.93 % BaCalcium 10.43 % CaSilicon 29.23 % SiHydrogen 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:whiteMore details...