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Manganite  
Current inventory:  0 gems
 

  
Manganite is named in allusion to its manganese content.

Discovered in 1827;   IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

Mn³⁺O(OH)

Manganese Oxide Hydroxide

Molecular Weight:

87.94 gm

Composition:

Manganese

62.47 %

Mn

89.76 %

Mn₂O₃

Hydrogen

1.15 %

H

10.24 %

H₂O

Oxygen

36.39 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Oxides

Strunz 8th Ed. ID:

4/F.06-70

Nickel-Strunz 10th Ed. ID:

4.FD.15

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
F : Hydroxides (without V or U)
D : Hydroxides with OH, without H₂O; chains of edge-sharing octahedra

Related to:

Trimorphous with Geitknechtite and Groutite

Varieties:

None

Synonyms:

Grau-Braunsteinerz, Gray Oxide of Manganese, Manganaise cristallisé, Manganèse oxydé metalloïde, Newkirkite, Prismatoidisches Mangan-Erz, Sphenomanganite

Crystal Data

Crystallography:

Monoclinic - Prismatic

Crystal Habit:

Crystals prismatic and striated || [001], short to long, to 7.5 cm; typically terminated by {001}, {h0l}, may be complex. In bundles, subparallel [001], fibrous; granular, massive.

Twinning:

Contact and penetration twins on {011}; lamellar on {100}.

Physical Properties

Cleavage:

{010} Perfect, {110} and {001} Good

Fracture:

Irregular/Uneven

Tenacity:

Brittle

Moh's Hardness:

4.0

Density:

4.29 - 4.34 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Dark steel-Gray to iron-Black; Red-Brown in transmitted light; in reflected light, Gray-White with Brownish tint, with blood-red internal reflections

Transparency:

Opaque, transparent on thin edges

Luster:

Sub-metallic

Refractive Index:

2.250 - 2.530  Biaxial  ( + )

Birefringence:

0.280

Dispersion:

Extreme; r > v

Pleochroism:

Weak, Faint; X = reddish brown; Z = red-brown

Anisotrophism:

Weak; Color in reflected light: gray-white with brown tint; Internal reflections: blood red; Bireflectance: distinct in grays

Occurances

Geological Setting:

Formed in low-temperature hydrothermal or hot-spring manganese deposits; replacing other manganese minerals in sedimentary deposits; a component in some clay deposits and laterites.

Common Associations:

Pyrolusite, Braunite, Hausmannite, Barite, Calcite, Siderite, Goethite

Common Impurities:

Fe, Ba, Pb, Cu, Al, Ca

Type Locality:

Manganese deposit, Ilfeld, Nordhausen, Harz Mts, Thuringia, Germany

Year Discovered:

1827

View mineral photos:

Manganite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Manganite was at one time a valuable manganese ore. It has been so heavily mined that it is now somewhat of a rarity and is considered a minor ore despite its high manganese content. Fine crystals were once found at Ilfeld, Harz Mountains and Ilmenau, Thuringia, Germany. Manganite is opaque black with sub-metallic luster and can be added to the list of black gems for collectors.

Manganite is found at many localities worldwide, but rarely well-crystallized. Fine crystals from Ilfeld, Harz Mountains, and Ilmenau, Thuringia, Germany. In the Botallack mine, St. Just, Cornwall; from Egremont, Cumbria; and at Upton Pyne, Exeter, Devonshire, England. From Granam, near Towie, Aberdeenshire, Scotland. At Bölet, near Karlsborg, Västergötland,Sweden. In the USA, good crystals from the Negaunee and Marquette districts, Marquette County, Michigan; in the Powell’s Fort mine, near Woodstock, Shenandoah County, Virginia; and at Lake Valley, Sierra County, New Mexico. From the Caland mine, Atikokan, Ontario, Canada. At Kuruman, Cape Province, South Africa.
 

  
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