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Formula: Mn2+(S4+O3)(H2O)3
Sulphite, orthorhombic paramorph of monoclinic
mikenewite,
manganese-bearing mineral
Crystal System: Orthorhombic
Specific gravity: 2.39 calculated
Streak: White
Colour: Colourless
Luminescence: Not fluorescent
Solubility: Insoluble in water and in ethyl alcohol, soluble in strong acids
Environments
Localities
At the type locality, the Gambatesa Mine, Reppia, Ne, Genoa, Liguria, Italy, the gravegliaite mineralisation
occurs at the surface of cavities along fractures crosscutting tephroite-,
bementite-, braunite-,
hausmannite- and hematite-
bearing layers in the chert. In the same fractures, but mainly in the
siliceous layers, also chalcocite and rarely
alabandite are locally found.
Although sulphur is lacking in the mineral phases of the
manganesiferous layers, sulphide phases, mainly
pyrite, are common both in the stratigraphically underlying
ophiolitic breccias and
in the overlying pelitic levels, providing sulphur for the formation of
gravegliaite. The wide range circulation of solutions, at temperature less
than 200°C, and commonly enriched in S2-, generally occurs along fractures formed during brittle, mainly
tensional, deformative phases, which arise after folding and metamorphic re-equilibration in the
prehnite-pumpellyite facies.
Gravegliaite appears as euhedral prismatic crystals up to 0.5 mm long, and as sheaf-like or radial aggregates, up
to 0.2 mm across
(Zeitschrift fUr Kristallographie 197.97-106).
Gravegliaite from the Gambatesa Mine - Image
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