Bementite (original) (raw)

A valid IMA mineral species - grandfathered

About BementiteHide

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Mn may be replaced by minor Fe, Mg and Zn.

Colour:

Brown, dark brown, golden brown, grayish-yellow

Lustre:

Sub-Vitreous, Resinous, Greasy

Specific Gravity:

2.9 - 3.1

Crystal System:

Monoclinic

Name:

Named for Clarence Sweet Bement [1843-1923] by George Augustus Koenig in 1887. Bement assembled the finest mineral collection in the USA. He also assembled the finest collection of U.S. coins and was interested in a variety of collectibles. Bement had a keen interest in Franklin, New Jersey minerals from whence his namesake was discovered.

Compare the very similar innsbruckite and the similar friedelite, as well as ganophyllite and parsettensite.

Raman spectroscopy or diffraction techniques are required to differentiate between bementite and innsbruckite (Krüger et al., 2014).

Unique IdentifiersHide

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Long-form identifier:

mindat:1:1:621:3

2b7111f4-8dc6-49da-be6b-6576fd1f0064

IMA Classification of BementiteHide

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Approved, 'Grandfathered' (first described prior to 1959)

Classification of BementiteHide

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9.EE.05

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

78.5.2.1

78 : Unclassified Silicates
5 :

14.17.8

14 : Silicates not Containing Aluminum
17 : Silicates of Mn

Mineral SymbolsHide

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As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.

Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.

Physical Properties of BementiteHide

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Sub-Vitreous, Resinous, Greasy

Colour:

Brown, dark brown, golden brown, grayish-yellow

Comment:

Lighter when fresh, weathering darker. Fresh material is transparent in splinters, weathering opaque.

Comment:

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

Cleavage:

Perfect
{001} perfect, {100} and {010} very good.

Density:

2.9 - 3.1 g/cm3 (Measured)

Comment:

Density does not support calculations for Z

Optical Data of BementiteHide

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RI values:

_n_α = 1.602 - 1.624 _n_β = 1.632 - 1.650 _n_γ = 1.632 - 1.650

δ = 0.030

Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.

Optical Extinction:

X ⊥ {001}.

Comments:

Colorless, pale yellow

Chemistry of BementiteHide

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Mindat Formula:

Mn7Si6O15(OH)8

Mn may be replaced by minor Fe, Mg and Zn.

Common Impurities:

Al,Fe,Zn,Mg,Ca

Crystallography of BementiteHide

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Crystal System:

Monoclinic

Cell Parameters:

a = 7.5 Å, b = 9.8 Å, c = 5.65 Å
β = 90°

Ratio:

a:b:c = 0.765 : 1 : 0.577

Unit Cell V:

415.28 ų (Calculated from Unit Cell)

Morphology:

Micaceous aggregates or plates are typical. Felted aggregates of fibers or plates.

Comment:

Better calculations obtained from Orthorhombic cell.

Crystal StructureHide

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ID	Species	Reference	Link	Year	Locality	Pressure (GPa)	Temp (K)
0001635	Bementite	Heinrich A R, Eggleton R A, Guggenheim S (1994) Structure and polytypism of bementite, a modulated layer silicate American Mineralogist 79 91-106		1994	0	293

CIF Raw Data - click here to close

X-Ray Powder DiffractionHide

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Radiation - Copper Kα

Data Set:

Data courtesy of RRUFF project at University of Arizona, used with permission.

Powder Diffraction Data:

Comments:

ICDD PDF 25-546.
Very similar to pattern of innsbruckite.

Geological EnvironmentHide

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Geological Setting:

Found in low-grade metamorphic manganese silicate deposits

Type Occurrence of BementiteHide

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General Appearance of Type Material:

Pale grayish yellow stellate masses, resembling karpholite or pyrophyllite.

Place of Conservation of Type Material:

Muséum Nationale d’Histoire Naturelle, Paris, France, number 115.290.

Geological Setting of Type Material:

Zinc-iron oxide ore deposit hosted in marble.

Associated Minerals at Type Locality:

Synonyms of BementiteHide

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Other Language Names for BementiteHide

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Common AssociatesHide

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Associated Minerals Based on Photo Data:

Related Minerals - Strunz-mindat GroupingHide

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Fluorescence of BementiteHide

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Other InformationHide

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Notes:

Decomposed by hot acid, but does not gelatinize.
Fuses easily to a black glass.
In closed tube it gives abundant water at a red heat, changing its color to dark brown.
In a borax bead, the bead remains colorless at first, gradually changing to the characteristic manganese color.

Health Risks:

No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

Internet Links for BementiteHide

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References for BementiteHide

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Reference List:

Krüger, H., Tropper, P., Haefeker, U., Kaindl, R., Tribus, M., Kahlenberg, V., Wikete, Ch., Fuchs, M. R. & Olieric, V. (2014): Innsbruckite, Mn33(Si2O5)14(OH)38 – a new mineral from the Tyrol, Austria. Mineralogical Magazine, 78, 1613-1627.

Localities for BementiteHide

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This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.

Locality ListHide

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- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for references and further information on this occurrence. ? - Indicates mineral may be doubtful at this locality. - Good crystals or important locality for species. - World class for species or very significant. (TL) - Type Locality for a valid mineral species. (FRL) - First Recorded Locality for everything else (eg varieties). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (e.g. from pseudomorphs).

All localities listed without proper references should be considered as questionable.