Glauconite

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Glauconite

Description

Glauconite at 100x (visible light left; UV light right)

A dull green mica mineral composed of hydrated potassium iron silicate. Glauconite, unlike other micas, usually occurs as pelletlike grains in marine environments and, hence, is sometimes called green sand. It is formed from the alteration of iron-bearing silicates by ocean water and organisms. Glauconite is found along the Atlantic coast of the North and South America and on the ocean floors. Powdered glauconite has been used as a Green earth pigment for paints.

Synonyms and Related Terms

green earth; Glaukonit (Deut.); glauconite (Fr., It., Port.); glaykofanis (Gr.); groene aarde (Ned.); glaukonit (Pol., Sven.); green sand; greensand

FTIR (MFA)

Glauconite, Harvard Mineralogical Museum.PNG

SEM

F367sem.jpg

EDS

F367edsbw.jpg


Physical and Chemical Properties

  • Crystals = monoclinic No apparent cleavage.
Composition (K,Na)(Fe3+,Al,Mg)2(Si,Al)4O10(OH)2
Mohs Hardness 2
Density 2.5-2.7 g/ml
Refractive Index 1.62

Resources and Citations

  • R. J. Gettens, G.L. Stout, Painting Materials, A Short Encyclopaedia, Dover Publications, New York, 1966 Comment: density 2.5-2.7 and ref.index.1.62
  • Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976