Trachyte

HA-18

Trachytes are an igneous volcanic rock with an aphanitic or porphyritic texture. Alkali feldspar, low amounts of plagioclase and quartz or a feldspathoid are common in trachytes.

Hand Sample: Aphanitic, light gray trachyte. On cut face, inclusions ranging from 0.8cm to 2cm in length with abundant vesicles less than 0.05cm in diameter can be observed.

Thin Section: Composed nearly entirely of glass material with some subhedral to euhedral plagioclase crystals that vary in size.

Sample collected January, 1969

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