Definition
Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock. It is produced when felsic lava extruded from a volcano cools rapidly with minimum crystal growth
Granite is a very hard, granular, crystalline igneous rock which consists mainly of quartz, mica, and feldspar and is often used as building stone
History
Origin
Ethiopia
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Discoverer
Obsius
Alexander von Humboldt
Etymology
From Latin obsidianus, misprint of Obsianus (lapis) (stone) of Obsius
From Italian granito, which means grained rock, from grano grain, and from Latin granum
Class
Igneous Rocks
Igneous Rocks
Sub-Class
Durable Rock, Medium Hardness Rock
Durable Rock, Hard Rock
Family
Group
Volcanic
Plutonic
Other Categories
Opaque Rock
Coarse Grained Rock, Opaque Rock