Lansfordite

Lansfordite is a hydrated magnesium  carbonate mineral with composition: MgCO3·5H2O. Landsfordite was discovered in 1888 in a coal mine in Lansford, Pennsylvania. It crystallizes in the monoclinic system and typically occurs as colorless to white prismatic crystals and stalactitic masses. It is a soft mineral, Mohs hardness of 2.5, with a low specific gravity of 1.7. It is transparent to translucent with refractive indices of 1.46 to 1.52.
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General Information:
 Chemical Formula:
MgCO3·5(H2O)
 Composition:
(Molecular Weight = 174.39 gm)
Magnesium 13.94 % Mg
Hydrogen 5.78 % H 
Carbon 6.89 % C 
Oxygen 73.40 % O 
 Empirical Formula:
Mg(CO3)·5(H2O)
Physical Properties:
 Cleavage:
[001] Perfect, [100] Distinct
 Color:
colorless or white.
 Density:
1.7
 Diaphaniety:
Transparent to Opaque
 Hardness:
2.5 - Finger Nail
 Luminescence:
Non-fluorescent.
 Luster:
Vitreous - Dull
 Streak:
white
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