Volcanic Glass In Thin Section

Daniel mayer volcanic glass is unstable and tends to change spontaneously devitrify from the glassy to the crystalline state in periods of time that are relatively short by geologic standards.

Volcanic glass in thin section. Volcanic rocks thin sections. Cristobalite may also form in the volcanic edifice by deposition and alteration from circulating hydrothermal fluids. These are photomicrographs very thin slices of rock seen in plane polarised light or between crossed polarisers when the colours seen are produced by interference of light.

It is typically light colored. The material takes on a stony appearance due to the presence of minutely crystalline aggregates. The thin section is suggesting what jemes s.

Volcanic glass can refer to the interstitial or matrix material in an aphanitic fine grained volcanic rock or can refer to any of several types of vitreous igneous rocks. Is a dark basaltic glass common in the groundmass of basalts or as thin shells on pillow lavas. Pumice is a volcanic rock that consists of highly vesicular rough textured volcanic glass which may or may not contain crystals.

Scoria is another vesicular volcanic rock that differs from pumice in having larger vesicles and thicker vesicle walls and being dark colored and denser. Such porphyritic rocks can be found either as volcanic or subvolcanic i e intrusive. Rhyolite from pitet belgium.

Volcanic glass in the lava may also devitrify again forming cristobalite or quartz if devitrification is influenced by hydrothermal fluids 10 12. Iceland agate volcanic rock definition of obsidian acid or granitic glass formed by the rapid cooling of lava without crystallization. Usually dark but transparent in thin pieces.

Volcanic glass dark reflective obsidian sitting atop gray rocks near the panum crater in mono county california. Rocks under the microscope. Beard mentioned a plutonic xenolith is a portphyritic groundmass.