General Information:
 Chemical Formula:
(Mg,Mn)2ZnSiO4(OH)2
 Composition:
(Molecular Weight = 255.41 gm)
Magnesium 14.27 % Mg
Manganese 10.75 % Mn
Zinc 25.60 % Zn
Silicon 11.00 % Si
Hydrogen 0.79 % H 
Oxygen 37.58 % O 
 Empirical Formula:
Mg1.5Mn2+0.5Zn(SiO4)(OH)2
 IMA Status:
Approved IMA 1976
Physical Properties:
 Cleavage:
[010] Good
 Color:
white or light pink.
 Density:
3.68
 Diaphaniety:
Translucent to Opaque
 Hardness:
4.5 - Between Fluorite and Apatite
 Luster:
Vitreous - Adamantine
 Streak:
white
More details...

The following video provides you with the correct English pronunciation of the word "Gerstmannite", to help you become a better English speaker.