Imogolite

phyllosilicate

halloysite

Formula: Al2SiO3(OH)4
Phyllosilicate (sheet silicate), allophane group
Specific gravity: 2.7
Hardness: 2 to 3
Streak: White
Colour: Yellowish white, light brownish yellow, blue, green, brown
Environments:

Sedimentary environments

Imogolite occurs principally in soils derived from volcanic ash. It has been found associated with allophane, halloysite, vermiculite, goethite, gibbsite and quartz. Imogolite has been observed in cracks in weathered plagioclase (Dana).

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