Definition
Rhyolite is a fine-grained igneous rock which is rich in silica
Scoria is a dark-colored extrusive igneous rock with abundant round bubble-like cavities
History
Origin
North America
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Discoverer
Ferdinand von Richthofen
Unknown
Etymology
From German Rhyolit, from Greek rhuax lava stream + lithos stone
From late Middle English (denoting slag from molten metal), from Greek skōria refuse, from skōr dung
Class
Igneous Rocks
Igneous Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Medium Hardness Rock
Family
Group
Volcanic
Volcanic
Other Categories
Coarse Grained Rock, Opaque Rock
Fine Grained Rock, Opaque Rock