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Formula: K(◻,Na)2(Mn,Fe,Mg)2[(Be,Al)3Si12]O30
Cyclosilicate (ring silicate), osumilite group,
manganese- and beryllium-
bearing mineral
Crystal System: Hexagonal
Specific gravity: 2.714 calculated
Hardness: 6
Streak: Pale orange
Colour: Yellow to orange
Luminescence: No fluorescence under UV
Common impurities: Na,Fe,Mg
Environments
Volcanic igneous environments
Metamorphic environments
Localities
At the type locality, the Caspar quarry, Ettringen, Vordereifel, Mayen-Koblenz, Rhineland-Palatinate, Germany,
almarudite occurs in the quarry at the Bellerberg volcano lava field, in metasomatised xenoliths in
leucite tephrite lava.
Associated minerals include tridymite,
sanidine, a clinopyroxene, an
amphibole, quartz,
hematite and braunite. The
almarudite forms euhedral, thick tabular crystals, maximum 1.5 mm across and 0.2 mm thick. The mineral is
vitreous and yellow to orange in colour, with a light orange streak
(CM 42.4.1241, HOM).
Almarudite from the Casper Quarry - Image
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