Hellandite-(Y)

General Information:
 Chemical Formula:
(Ca,Y)6(Al,Fe+++)Si4B4O20(OH)4
 Composition:
(Molecular Weight = 915.92 gm)
Calcium 17.50 % Ca
Yttrium 19.41 % Y 
Aluminum 2.21 % Al
Iron 1.52 % Fe
Silicon 12.27 % Si
Boron 4.72 % B 
Hydrogen 0.44 % H 
Oxygen 41.92 % O 
 Empirical Formula:
Ca4Y2Al0.75Fe3+0.25Si4B4O20(OH)4
 Environment:
Pegmatite
 IMA Status:
Approved IMA 1987
 Locality:
Kragero, Telemark, norway.
Physical Properties:
 Cleavage:
None
 Color:
green yellow, grayish black, reddish brown, or black.
 Density:
3.7
 Diaphaniety:
Translucent to subtranslucent
 Habits:
Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline)., ,
 Hardness:
5.5 - Knife Blade
 Luster:
Vitreous - Greasy
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