Ternesite

General Information:
 Chemical Formula:
Ca5(SiO4)2SO4
 Composition:
(Molecular Weight = 480.62 gm)
Calcium 41.69 % Ca
Silicon 11.69 % Si
Sulfur 6.67 % S 
Oxygen 39.95 % O 
 Empirical Formula:
Ca5(SiO4)2(SO4)
 Environment:
In calcium-rich xenoliths in leucite tephrite lava.
 IMA Status:
Approved IMA (Dana # Added)
 Locality:
The Ettringer Bellerberg, near Mayen, Eifel, Germany.
 Name Origin:
For Mr. B. Ternes of Mayen, Germany, who found the mineral and provided specimens for the study.
Physical Properties:
 Cleavage:
None
 Color:
colorless or bright blue.
 Density:
2.94 - 2.98, Average = 2.96
 Diaphaniety:
Transparent
 Habits:
Radial - Crystals radiate from a center without producing stellar forms (e.g. stibnite), Aggregates - Made of numerous individual crystals or clusters.,
 Hardness:
4.5 - Between Fluorite and Apatite
 Luminescence:
Non-fluorescent.
 Luster:
Vitreous (Glassy)
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