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
Mylonite is a metamorphic rock formed by ductile deformation during intense shearing encountered during folding and faulting, a process termed cataclastic or dynamic metamorphism
History
Origin
Ethiopia
New Zealand
Discoverer
Obsius
Unknown
Etymology
From Latin obsidianus, misprint of Obsianus (lapis) (stone) of Obsius
From Greek mulōn mill + -ite
Class
Igneous Rocks
Metamorphic Rocks
Sub-Class
Durable Rock, Medium Hardness Rock
Durable Rock, Medium Hardness Rock
Family
Group
Volcanic
-
Other Categories
Opaque Rock
Fine Grained Rock, Opaque Rock