Ettringite is not generally facetable; any cut stone would be considered an extreme rarity. South African material has yielded minute stones, some of which may have been labeled sturmanite.
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|Crystallography||Hexagonal; usually flattened hexagonal dipyramids; sometimes prismatic, fibrous.|
|Colors||Colorless; transparent to translucent, milky.|
|Stone Sizes||Material from Ettringen and Franklin is microscopic. A 2.5 carat pale yellow ettringite was faceted from material found in the center of a mass of sturmanite from South Africa. This may be the largest known for the species.|
|Pleochroism||None; colorless in transmitted light; dehydrates and turns white.|
Series to Sturmanite.
Optics: o= 1.491; e= 1.470.
Occurrence: At type locality (Ettringen, Rhine Province, Germany) in cavities of metamorphosed limestone inclusions in alkaline igneous rocks. Also in metamorphosed limestones.
Ettringen, Germany: In tiny crystals.
Franklin, New Jersey: Minute crystals.
South Africa: Associated with sturmanite at the Jwaneng mine, near Hotazel. The sturmanite forms yellowish coatings, with ettringite cores.
Comments: Ettringite is not generally facetable; any cut stone would be considered an extreme rarity. South African material has yielded minute stones, some of which may have been labeled sturmanite.
Name: After the locality in Germany.