Bementite
Current inventory:  0 gems
 

  
Bementite is named for Clarence Sweet Bement [1843-1923] by George Augustus Koenig in 1887. Bement had a keen interest in Franklin, New Jersey minerals from whence his namesake was discovered.

Discovered in 1887;   IMA status: Valid (IMA approved 1963)

Chemistry

Chemical Formula:

Mn₅Si₄O₁₀(OH)₆

Manganese Silicate Hydroxide

Molecular Weight:

1,018.08 gm

Composition:

Manganese

43.17 %

Mn

55.74 %

MnO

Silicon

16.55 %

Si

35.41 %

SiO₂

Hydrogen

0.99 %

H

8.85 %

H₂O

Oxygen

39.29 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/H.28-90

Nickel-Strunz 10th Ed. ID:

9.EE.05

9 : SILICATES (Germanates)
E : Phyllosilicates
E : Single tetrahedral nets of 6-membered rings connected by octahedral nets or octahedral bands

Related to:

Compare to the similar Friedelite

Varieties:

None

Synonyms:

Bementite (of Koenig)

Crystal Data

Crystallography:

Monoclinic - Prismatic

Crystal Habit:

Radiated or stellate with minute foliated structure; compact, hornlike forms; massive granular; in intricate intergrowths with other minerals.

Twinning:

None

Physical Properties

Cleavage:

Perfect on {001}, very Good on {100} and {010}

Fracture:

Conchoidal

Tenacity:

Flexible

Moh's Hardness:

6.0; Sometimes given as variable 4-6, softer mineral due to alteration.

Density:

2.90 - 3.10 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Brown, dark Drown, Golden Brown, Grayish-Yellow

Transparency:

Translucent to Sub-Translucent

Luster:

Sub-Vitreous, Resinous, Greasy, Pearly on perfect cleavage

Refractive Index:

1.602 - 1.650  Biaxial ( - )

Birefringence:

0.026 - 0.030

Dispersion:

Weak

Pleochroism:

Weak; colorless, pale yellow

Occurances

Geological Setting:

Layered parallel to the walls of secondary veins of calcite in a metamorphosed stratiform zinc orebody (Franklin, New Jersey, USA); intimately intergrown with other manganese minerals (Olympic Peninsula, Washington, USA).

Common Associations:

Calcite, Willemite (Franklin, New Jersey, USA); Alleghanyite, Barite, Braunite, Calcite, Grossular, Hausmannite, Jacobsite, Johannsenite, (Olympic Peninsula, Washington, USA); Hausmannite, Inesite, Rhodochrosite (Hale Creek, California, USA).

Common Impurities:

Al, Fe, Zn, Mg, Ca

Type Locality:

Trotter Mine (Lehigh Mine), Franklin, Franklin Mining District, Sussex Co., New Jersey, USA

Year Discovered:

1887 (IMA approved 1963)

View mineral photos:

Bementite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Bementite is a rare Manganese Silicate mineral that is found as radiated or stellate crystals to massive granular forms and often found in intricate intergrowths with other minerals.

Bementite localities are in the USA, at Franklin, Sussex County, New Jersey; in Washington, on the Olympic Peninsula, an ore mineral at a number of small deposits in Clallan, Jefferson, and Mason Counties; from Ray, Pinal County, Arizona; at Hale Creek, Trinity County, California; and from the Black Diablo mine, Black Diablo district, Pershing County, Nevada. In the Treburland mine, Altarnun, Cornwall, and near Chillaten, Devon, England. From Langbån, Värmland, Sweden. In Russia, at a number of poorly-defined localities. In the Tokuzawa mine, Fukushima Prefecture; the Ichinomata mine, Kumamoto Prefecture; and at Kunimiyama, Kochi Prefecture, Japan. In the Wessels mine, near Kuruman, Cape Province, South Africa.
 

  
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