Inesite

minerals

todorokite

neotocite

orientite

Formula: Ca2Mn2+7Si10O28(OH)2.5H2O
Inosilicate (chain silicate)
Specific gravity: 3.03 to 3.04
Hardness: 5½ to 6
Streak: White
Colour: Rose-red, pink, orange-pink, orange-red-brown
Solubility: Soluble in acids
Common impurities: Fe,Al,Mg,K
Environments

Sedimentary environments
Metamorphic environents
Hydrothermal environents

Inesite occurs in manganese deposits. The largest deposits are sedimentary, the result of chemical precipitation of manganese during the slow accumulation of sediment in marine environments. The beds are then brought nearer to the surface through mountainbuilding cycles.
Other deposits are present-day beds of concentrically layered nodules on areas of the deep ocean floor and near-surface beds resulting from secondary concentration of manganese through the deep weathering processes that produce lateritic soils.
Inesite also occurs in hydrothermal veins and as deposition resulting from volcanic action on the ocean floor (R&M 86-3.250-260).

Localities

At the Broken Hill lode, Yancowinna county, New South Wales, Australia, inesite occurs in fracture-filled veins. Marginal to the veins silicates in the wall rock are extensively altered to patches of fine-grained chlorite. Acicular crystals of inesite, generally less than l-2 cm long, form radiating aggregates together with calcite in the veins. In places veins consisting almost wholly of inesite become, within a few feet, calcite-rich with minor inesite toward the centre, and in some places inesite is encrusted with apophyllite. Rarely, single crystals of inesite up to 1 cm have been found lining cavities (AM 53.1614-1634 ).

At the Southern operations mine (Consolidated Zinc Mine, NBHC Mine), Broken Hill, Broken Hill district, Yancowinna county, New South Wales, Australia, fine specimens of inesite, many sprinkled with fluorapophyllite crystals, lined the pockets in the inesite-calcite veins as hemispheres to 6 cm across, “bowties” just over 1 cm, and, occasionally, single crystals to 1 cm (R&M 86-3.250-260). Composite inclusions of galena - sphalerite - pyrite - chalcopyrite, up to 3 mm across, occur disseminated through the inesite-bearing veins. Other associated minerals include calcite, apophyllite and chlorite (AM 53.1614-1634 ).

At the Fengjiashan Mine, Daye county, Huangshi, Hubei, China, fine inesite specimens occurred on matrix or on clusters of quartz crystals. Individual quartz crystals to 1.5 cm with one side preferentially coated with red-orange inesite have been found. Some specimens are completely coated with apophyllite. Additional associated minerals include calcite, pyrite, hubeite, ilvaite and hematite (R&M 86-3.250-260).

At the type locality, Hilfe Gottes mine, Oberscheld, Dillenburg, Lahn-Dill, Giessen Region, Hesse, Germany, inesite was found embedded in calcite veins (R&M 86-3.250-260).

At the Cirotan mine, Cikotok Gold District, Banten Province, Java, Indonesia, inesite is found only in small fibrous aggregates in breccia. The breccia pieces have a stony or sulphide core (often pyrite) that is surrounded by rhodonite that transitions into rhodochrosite, followed by a rim of increasingly coarse-grained quartz-sulphide mixture, then chlorite-sulphide mixture, and finally more quartz with muscovite variety illite and calcite. The inesite is sometimes present as a phase between the rhodonite and rhodochrosite zones (R&M 86-3.250-260).

At Tambang Sawah, Rejang Lebong District, Bengkulu Province, Indonesia, inesite occurred in low temperature hydrothermal gold and silver bearing quartz veins, with gold variety electrum and uytenbogaardtite (R&M 86-3.250-260).

Much of the Japanese inesite is confined to low-temperature gold and silver bearing quartz veins cutting through young volcanics (R&M 86-3.250-260).

At the Todoroki mine, Yoichi District, Shiribeshi Subprefecture, Hokkaidō Prefecture, Japan, inesite as very small needles forming botryoidal masses was present, in places hydrothermally altered to todorokite (R&M 86-3.250-260).

The Noda-Tamagawa mine, Noda-mura, Kunohe-gun, Iwate Prefecture, Japan, is hosted in very large bedded manganese deposits exhibiting a strongly zoned area of contact metamorphism where manganese silicate minerals including inesite have been formed from primary rhodochrosite (R&M 86-3.250-260).

At the Kawazu mine, Rendaiji, Shimoda City, Shizuoka Prefecture, Japan, inesite formed as tufts of crystals to 1 cm filling cavities in quartz veins or as massive veins penetrating the country rock. Crystals could also form radial or spherical aggregates, fibrous sheaves, and sprays associated with rhodochrosite and neotocite (R&M 86-3.250-260).

At the San Cayetano mine, Rancho Ventana, Mun. de Tamazula, Durango, Mexico, inesite tufts of radiating crystals roughly 0.5 cm in length have been found almost completely enclosed in calcite (R&M 86-3.250-260).

Martha Mine, Waihi, Hauraki District, Waikato Region, New Zealand, is the site of an extensive, low-temperature gold and silver bearing quartz vein network. Fibrous inesite has been found here from a vug in a quartz vein and attached to altered wall rock or quartz variety amethyst veining (R&M 86-3.250-260).

At the Wessels mine, Hotazel, Kalahari manganese field, Northern Cape, South Africa, inesite is associated with datolite, pectolite, apophyllite, ruizite, orientite and quartz (HOM). The Kalahari manganese district is a huge, extremely old, sedimentary-type manganese deposit. Early specimens of inesite comprised crystals to 1 cm in tightly packed clusters with quartz and orientite. Perched on their tips were a sequence of datolite followed by pectolite followed by an apophyllite-group mineral and ruizite. Later individual crystals to 2 cm were found. Sprays of natrolite to 2.5 cm adorned some specimens; others had sprays or hemispheres of xonotlite, and botryoidal datolite served as a base for many of them. Crystals of an apophyllite-group mineral and rare orlymanite were also possible associates (R&M 86-3.250-260).

At the N'Chwaning II Mine, N'Chwaning Mines, Kuruman, Kalahari manganese field, Northern Cape, South Africa, a zone of breccia has been found; thousands of breccia chunks and plates were recovered, each completely and uniformly coated with thin laths to short needles of inesite about 3 mm in length. A second distinctive occurrence at N’Chwanning II was the association of crystallised orange prehnite with orange-red inesite (R&M 86-3.250-260).

At the Harstigen Mine, Pajsberg, Persberg ore district, Filipstad, Värmland County, Sweden, fibrous inesite has been found associated with rhodonite and garnet as crack fillings and in calcite veins in iron ore (R&M 86-3.250-260).

At Långban, Filipstad, Värmland County, Sweden, inesite crystals have been found as radial sprays on a white background of calcite or baryte further contrasted with a dark hematite matrix. Långban specimens might also show patches of associated andradite or native lead (R&M 86-3.250-260).

At a site in Napa County, California, USA, likely northeast of San Francisco in the northern part of the county, a specimen of aggregates of thin, radiating blades of inesite embedded in a matrix of bementite has been found, with veinlets of calcite cutting through the bementite (R&M 86-3.250-260).

At Hale Creek Mine, Mad River Rock, Coastal Range, Trinity county, California, USA, inesite is associated with rhodochrosite, bementite and hausmannite (HOM, Dana) in a calcite-filled vein. When the calcite was etched away inesite crystals of very high quality were revealed. Occasionally, baryte crystals and native copper are found with the inesite (R&M 86-3.250-260).

The Equity mine Creede District, Mineral county, Colorado, USA produced inesite spherules to 2 cm wide and fan-shaped aggregates of needlelike crystals in late-stage hydrothermal veinlets to 5 cm thick. Associated minerals are quartz, common sulphides and rhodochrosite (R&M 86-3.250-260).

At the Crescent mine, Lake Crescent, Clallam county, Washington, USA, inesite is associated with bementite and hausmannite (Dana).

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