Definition
Definition
Anthracite is a type of sedimentary rock which is hard and is variety of coal that has high luster
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
History
Origin
Pennsylvania, U.S.
Ethiopia
Discoverer
Unknown
Obsius
Etymology
From Greek anthrakites, from anthrax, anthrak meaning coal
From Latin obsidianus, misprint of Obsianus (lapis) (stone) of Obsius
Class
Metamorphic Rocks
Igneous Rocks
Sub-Class
Durable Rock, Soft Rock
Durable Rock, Medium Hardness Rock
Family
Group
Not Applicable
Volcanic
Other Categories
Coarse Grained Rock, Fine Grained Rock, Medium Grained Rock, Opaque Rock
Opaque Rock
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