Pitchstone - Wikipedia, the free encyclopedia
Pitchstone is a dull black glassy volcanic rock formed when lava cools swiftly. It is similar to but coarser than obsidian. The ridge of An Sgurr on the Isle of Eigg was originally formed as a lava f...
en.wikipedia.org/wiki/Pitchstone
|
|
A good rule of thumb is that fine grained or aphanitic rocks are dull appearing, while phaneritic rocks are brighter or shinier (of course be careful of a glassy rock like obsidian). ... Pure volcanic glass is known as obsidian (see photo).
|
geology.csupomona.edu/alert/igneous/texture.htm
|
|
|
|
Thus, most field classifications of volcanic rocks rely on the few phenocrysts we can see or the rock's color. The latter can be especially unreliable, but often it is the only clue me have. We shall attempt to rely on texture, color and phenocryts to identify our volcanic rock specimens.
|
geology.csupomona.edu/alert/igneous/ignrxs.htm
|
|
|
|
MSN home Mail My MSN ... encarta greeting cards ... 1. black shiny volcanic rock: a hard, black, often glassy, volcanic rock. It was produced by the partial melting of the Earth's mantle.
|
encarta.msn.com/dictionary_1861589073/basalt.html
|
|
|
Andesite is a gray to black volcanic rock with between about 52 and 63 weight percent silica (SiO2). Andesites contain crystals composed primarily of plagioclase feldspar and one or more of the minerals pyroxene (clinopyroxene and orthopyroxene) and lesser amounts of hornblende.
|
vulcan.wr.usgs.gov/Glossary/volcano_terminology.html
vulcan.wr.usgs.gov/Glossary/volcano_terminology.html
|
|
|
www-odp.tamu.edu/publications/193_IR/chap_04/c4_f34.htm
|
|
|
www-odp.tamu.edu/publications/193_IR/chap_04/c4_f54.htm
|
|
Igneous Rock Classification ... Texture vs. composition ... Conditions needed to produce ultramafic flows do not exist in nature at this time...
|
jersey.uoregon.edu/~mstrick/AskGeoMan/IgRxChart.html
|
|
Although widespread, their distribution is patchy and their intensities are highly variable, reflecting the complexity of the original textures in glassy volcanic rocks.
|
econgeol.geoscienceworld.org/cgi/content/abstract/96/5/...
econgeol.geoscienceworld.org/cgi/content/abstract/96/5/973
|
|
