Ternesite

ternesite

ellestadite

rondorfite

leucite

Images

Formula: Ca₅(SiO₄)₂(SO₄)
Nesosilicate (insular SiO₄ groups)
Crystal System: Orthorhombic
Specific gravity: 2.94 measured, 2.97 calculated
Hardness: 4½ to 5
Streak: White
Colour: Pale blue, brown, light green, colourless
Luminescence: Not fluorescent under UV
Environments

Volcanic igneous environments

Localities

At the type locality, the Caspar quarry, Ettringen, Vordereifel, Mayen-Koblenz, Rhineland-Palatinate, Germany, ternesite occurs as prismatic crystals to 0.2 mm in length and 0.05 mm in diameter, radially arranged into bright blue aggregates in calcium-rich xenoliths in Quaternary (2.6 million years ago to the present) leucite tephrite lava, associated with ellestadite (Mindat).
Ternesite is also reported as one of the minerals associated with rondorfite at this locality (AM 89.1576).

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