Acuminite

Acuminite (or Acuminit or Acuminita) Sr[AlF4(OH)(H2O)] is a mineral of strontium, aluminium, fluorine, oxygen, and hydrogen. Its name comes from the Latin word acumen, meaning "spear point". Its Mohs scale rating is 3.5.
See more at Wikipedia.org...

General Information:
 Chemical Formula:
SrAlF4(OH)·(H2O)
 Composition:
(Molecular Weight = 225.62 gm)
Strontium 38.84 % Sr
Aluminum 11.96 % Al
Hydrogen 1.34 % H 
Oxygen 14.18 % O 
Fluorine 33.68 % F 
 Empirical Formula:
SrAlF4(OH)·(H2O)
 IMA Status:
Approved IMA 1985
 Locality:
TL: Greenland, Ivigtut
Physical Properties:
 Cleavage:
[???] Perfect
 Color:
colorless.
 Density:
3.295
 Diaphaniety:
Transparent
 Hardness:
3.5 - Copper Penny
 Luster:
Vitreous (Glassy)
 Streak:
white
More details...