Jahnsite-(CaMnMg)

General Information:
 Chemical Formula:
CaMnMg2Fe+++2(PO4)4(OH)2·8(H2O)
 Composition:
(Molecular Weight = 813.34 gm)
Calcium 4.93 % Ca
Magnesium 5.98 % Mg
Manganese 6.75 % Mn
Iron 13.73 % Fe
Phosphorus 15.23 % P 
Hydrogen 2.23 % H 
Oxygen 51.15 % O 
 Empirical Formula:
CaMn2+Mg2Fe3+2(PO4)4(OH)2·8(H2O)
 IMA Status:
Approved IMA
 Locality:
Tip Top pegmatite, Custer, South Dakota, USA.
 Name Origin:
Named for Richard H. Jahns (1915-1983), mineralogist and pegmatite expert, Stanford University, Palo Alto, California, USA.
Physical Properties:
 Cleavage:
[001] Good
 Color:
brown, purplish brown, yellow, yellow orange, or greenish yellow.
 Density:
2.706 - 2.718, Average = 2.71
 Diaphaniety:
Transparent to Translucent
 Hardness:
4 - Fluorite
 Luster:
Vitreous - Adamantine
 Streak:
white
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