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Brammallite



Brammallite
CategoryMineral
Chemical formulaNa0.65Al2.0Al0.65Si3.35O10(OH)2
Identification
ColorWhite
Mohs Scale hardness2½ - 3
StreakWhite

Brammallite is a sodium rich analogue illite. First found in 1943 in Llandybie, Carmarthenshire, Wales, it is named after British geologist and mineralogist Alfred Brammall (1879-?).

Additional recommended knowledge

Believed to be a degradation product of paragonite, like illite it is a non-expanding, clay-sized, micaceous mineral. Brammallite is a phyllosilicate or layered silicate. Structurally, brammallite is quite similar to muscovite or sericite with slightly more silicon, magnesium, iron, and water and slightly less tetrahedral aluminium and interlayer potassium.

The chemical formula is given as (Na,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)].[1]

It occurs as aggregates of small monoclinic dark grey-brown crystals. Due to the small size, positive identification usually requires x-ray diffraction analysis.

See also

References

  1. ^ http://www.mindat.org/min-816.html


 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Brammallite". A list of authors is available in Wikipedia.
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