hyalopilitic

Adjective.  A textural term used in petrographic classification of volcanic rocks, referring to a volcanic rock groundmass, which is visible only under magnification with a petrographic microscope, that contains a mixture of very fine-grained mineral crystals either mixed with natural volcanic glass, or surrounded by thin bands of volcanic glass.

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This entry was last updated on RefTopia from its source on 3/20/2012.