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Formula: Ca3Mn3+2(SiO4)2(OH)4
Nesosilicate (insular SiO4 groups),
henritermierite group,
garnet supergroup,
manganese-bearing mineral
Crystal System: Tetragonal
Specific gravity: 3.34 measured, 3.40 calculated
Streak: White
Colour: Clove-brown to apricot-brown; lemon-yellow to pale yellow in thin section.
Solubility: Slowly dissolved by cold hydrochloric acid, easily by warm hydrochloric acid, leaving a silica residue.
Nitric acid attacks henritermierite superficially with formation of black MnO2
(AM 54.1739)
Common impurities: Fe
Environments
Localities
At the type locality, the Tachgagalt mine, Tansifite Caïdat, Agdz Cercle, Zagora Province, Drâa-Tafilalet Region,
Morocco, henritermierite occurs in the manganese ore deposit in
aggregates of small grains up to 0.5 mm; mostly about 0.2 mm across. The grains
fill interstices between crystals of marokite,
hausmannite, and rare
gaudefroyite. Calcite is
commonly present also
(AM 54.1739).
At the N'Chwaning Mines, Kuruman, Kalahari manganese field, Northern Cape, South Africa, henritermierite is
associated with hausmannite,
manganite, hematite,
calcite, baryte and
andradite
(HOM).
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