epidote

Epidote is a calcium aluminium iron sorosilicate mineral, Ca2(Al, Fe)3(SiO4)3(OH), crystallizing in the monoclinic system. Well-developed crystals are of frequent occurrence: they are commonly prismatic in habit, the direction of elongation being perpendicular to the single plane of symmetry. The faces are often deeply striated and crystals are often twinned. Many of the characters of the mineral vary with the amount of iron present for instance, the color, the optical constants, and the specific gravity (3.33). The hardness is 6.5. The color is green, grey, brown or nearly black, but usually a characteristic shade of yellowish-green or pistachio-green. The pleochroism is strong, the pleochroic colors being usually green, yellow and brown. Clinozoisite is white or pale rose-red variety containing very little iron, thus having the same chemical composition as the orthorhombic mineral zoisite.
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n. epidote

(n.)
A mineral, commonly of a yellowish green (pistachio) color, occurring granular, massive, columnar, and in monoclinic crystals. It is a silicate of alumina, lime, and oxide of iron, or manganese.
  

General Information:
 Chemical Formula:
Ca2(Fe+++,Al)3(SiO4)3(OH) = Ca2(Fe,Al)Al2(SiO4)(Si2O7)O(OH)
 Composition:
(Molecular Weight = 519.30 gm)
Calcium 15.44 % Ca
Aluminum 3.90 % Al
Iron 24.20 % Fe
Silicon 16.22 % Si
Hydrogen 0.19 % H 
Oxygen 40.05 % O 
 Empirical Formula:
Ca2Fe3+2.25Al0.75(SiO4)3(OH)
 Environment:
Contact metamorphic rocks.
 Locality:
Common world wide.
 Name Origin:
From the Greek epidosis - "addition."
Physical Properties:
 Cleavage:
[001] Perfect
 Color:
yellowish green, brownish green, black, yellow, or gray.
 Density:
3.3 - 3.6, Average = 3.45
 Diaphaniety:
Transparent to translucent to opaque
 Habits:
Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline)., Fibrous - Crystals made up of fibers., Massive - Uniformly indistinguishable crystals forming large masses.
 Hardness:
7 - Quartz
 Luminescence:
None.
 Luster:
Vitreous (Glassy)
 Streak:
grayish white
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epidote
danh từ (khoáng chất) epidot
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