Overite

Segelerite is a complex phosphate mineral with formula CaMgFe3+OH(PO4)2·H2O. It occurs in pegmatites and forms striking green or chartreuse crystals. It was discovered in 1974 in the Black Hills of South Dakota by an amateur mineralogist from New York, Curt G. Segeler (1901-1989), after whom it is named.
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General Information:
 Chemical Formula:
CaMgAl(PO4)2(OH)·4(H2O)
 Composition:
(Molecular Weight = 370.38 gm)
Calcium 10.82 % Ca
Magnesium 6.56 % Mg
Aluminum 7.28 % Al
Phosphorus 16.73 % P 
Hydrogen 2.45 % H 
Oxygen 56.16 % O 
 Empirical Formula:
CaMgAl(PO4)2(OH)·4(H2O)
Physical Properties:
 Cleavage:
[010] Perfect, [100] Indistinct
 Color:
colorless or light green.
 Density:
2.53
 Diaphaniety:
Transparent to Translucent
 Hardness:
3.5-4 - Copper Penny-Flourite
 Luster:
Vitreous (Glassy)
 Streak:
white
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