Formula: Ca4Mn2+3Si8O20(OH)6.2H2O
Phyllosilicate (sheet silicate), gyrolite group, manganese-bearing mineral, 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

Hydrothermal environments


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).

Back to Minerals