Formula: Ca4Mn2+3Si8O20(OH)6.2H2O
Phyllosilicate (sheet silicate), gyrolite group, approved in 1990
Specific gravity: 2.7 to 2.8
Hardness: 4 to 5
Streak: Light brown
Colour: Dark brown
Common impurities: Al,Fe,Mg,Na
Environments
Localities
The type locality is the Wessels Mine, Hotazel, Kalahari manganese field, Northern Cape, South Africa.
Orlymanite has been found in only one specimen, labeled as being from the Wessels mine. It occurs as part of an
assemblage that resembles a 1.5-2.0 cm thick vein in manganese ore, consisting
of dark brown orlymanite spherules,
2 to 3 mm in diameter, intermixed with a very light brown aggregate of micaceous grains of impure orlymanite that
resembles bementite in physical appearance. Massive
inesite and earthy hematite are sparsely
distributed within this light brown material. Both surfaces of the assemblage consist of the light brown material, abundant
spherules of inesite 1.0 cm in diameter, and minor
calcite. The boundary between the inesite
and orlymanite had well-defined prismatic inesite crystals extending into
the massive orlymanite, consistent with a vein assemblage in which
inesite was an earlier phase
(AM 75.923-927).
Orlymanite has also been reported from the N'Chwaning II Mine, N'Chwaning Mines, Kuruman, Kalahari manganese field,
Northern Cape, South Africa
(Mindat).
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