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
Troctolite is a mafic intrusive rock type. It consists essentially of major but variable amounts of olivine and calcic plagioclase along with minor pyroxene. It is an olivine-rich anorthosite, or a pyroxene-depleted relative of gabbro
History
Origin
Ethiopia
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Discoverer
Obsius
Christian Leopold von Buch
Etymology
From Latin obsidianus, misprint of Obsianus (lapis) (stone) of Obsius
From German Troklotit, from Greek trōktēs, a marine fish (taken to be trout)
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