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Silicate

Alumino-oxy-rossmanite

Al₃Al₆(Si₅AlO₁₈)(BO₃)₃(OH)₃O
Hardness7
Crystal systemHexagonal
ClassSilicate
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Alumino-oxy-rossmanite

Alumino-oxy-rossmanite is an IMA-recognized mineral species in the silicate class, with the chemical formula Al₃Al₆(Si₅AlO₁₈)(BO₃)₃(OH)₃O.

It crystallizes in the hexagonal crystal system (space group R3m). It is a member of the Tourmaline structural group.

Key properties: Mohs hardness 7; specific gravity 3.07; White streak; Vitreous luster; optically uniaxial.

IMA symbol Aorsm, IMA status: approved, named in 2020.

An early magmatic Al-rich oxy-tourmaline indicative of high-temperature in a relatively dry environment, which is poor in Li and F, in pegmatitic in amphibolite and biotite-rich paragneiss.

It is found associated with Quartz, albite, microcline, apatite, beryl, schorl.

Prefixes identify dominant composition of the Y and W sites in a tourmaline related to rossmanite which honors George R. Rossman, Professor of Mineralogy, California Institute of Technology.

Index entry. This entry combines official IMA/RRUFF species data with published physical-property data — a full written entry hasn’t been published yet. Browse more A minerals or help write this entry.