This is the polished rhyolite sphere with fluorite. Diameter 2.3″ (58mm). Weight – 9.5oz (270 grams). Origin: Russia, Siberia.
Some information about rhyolite:
Rhyolite is an extrusive igneous rock, formed from magma rich in silica that extruded from a volcanic vent to cool quickly on the surface rather than slowly in the subsurface. It is generally light in color due to its low content of mafic minerals. It typically very fine-grained or glassy.
An extrusive igneous rock is classified as rhyolite when quartz constitutes 20% to 60% by volume of its total content of quartz, alkali feldspar, and plagioclase (QAPF) and alkali feldspar makes up 35% to 90% of its total feldspar content.
The name rhyolite was introduced into geology in 1860 by the German traveler and geologist Ferdinand von Richthofen from the Greek word rhýax (“a stream of lava”) and the rock name suffix “-lite” (More information about rhyolite).
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