Dickite

Dickite is a phyllosilicate clay mineral, with the same composition as kaolinite, nacrite, and halloysite, but with a different crystal structure (polymorph). Its chemical composition is Al2Si2O5(OH)4. It occurs with other clays and requires x-ray diffraction for its positive identification. Dickite is an important alteration indicator in hydrothermal systems as well as occurring in soils and shales. It takes its name from Allan Brugh Dick (1833-1926), the Scottish metallurgical chemist who first described it.
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General Information:
 Chemical Formula:
Al2Si2O5(OH)4
 Composition:
(Molecular Weight = 258.16 gm)
Aluminum 20.90 % Al
Silicon 21.76 % Si
Hydrogen 1.56 % H 
Oxygen 55.78 % O 
 Empirical Formula:
Al2Si2O5(OH)4
 Name Origin:
Named after the Scottish chemist, A. B. Dick.
Physical Properties:
 Cleavage:
[001] Perfect
 Color:
blue, colorless, gray, yellow brown, or white.
 Density:
2.6
 Diaphaniety:
Subtranslucent to opaque
 Habits:
Earthy - Dull, clay-like texture with no visible crystalline affinities, (e.g. howlite)., ,
 Hardness:
1.5-2 - Talc-Gypsum
 Luster:
Pearly
 Streak:
white
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B: (Kimia) dikit
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