Antigorite

Serpentine is a group of common rock-forming hydrous magnesium iron phyllosilicate ((, Fe)3O) minerals; it may contain minor amounts of other elements including chromium, manganese, cobalt and nickel. In mineralogy and gemology, serpentine may refer to any of 20 varieties belonging to the serpentine group. Owing to admixture, these varieties are not always easy to individualize, and distinctions are not usually made. There are three important mineral polymorphs of serpentine: antigorite, chrysotile and lizardite.
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General Information:
 Chemical Formula:
(Mg,Fe++)3Si2O5(OH)4
 Composition:
(Molecular Weight = 300.77 gm)
Magnesium 18.18 % Mg
Iron 13.93 % Fe
Silicon 18.68 % Si
Hydrogen 1.34 % H 
Oxygen 47.88 % O 
 Empirical Formula:
Mg2.25Fe2+0.75(Si2O5)(OH)4
 IMA Status:
Approved IMA 1962
 Locality:
Antigorio, Italy
 Name Origin:
Named after its locality. From the Latin, serpens - "snake."
Physical Properties:
 Cleavage:
[001] Good
 Color:
green, gray, bluish gray, brown, or black.
 Density:
2.5 - 2.6, Average = 2.54
 Diaphaniety:
Translucent to Subopaque
 Habits:
Platy - Sheet forms (e.g. micas)., Massive - Uniformly indistinguishable crystals forming large masses., Scaly - Morphology like fish scales.
 Hardness:
3.5-4 - Copper Penny-Flourite
 Luster:
Vitreous - Greasy
 Streak:
greenish white
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ANTIGORITE

B: (Kimia) antigorit
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