Definition
Oil Shale is a fine-grained sedimentary rock from which oil is extracted
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
-
Ethiopia
Discoverer
Unknown
Obsius
Etymology
From Old English scealu in its base sense of thing that divides or separate
From Latin obsidianus, misprint of Obsianus (lapis) (stone) of Obsius
Class
Sedimentary Rocks
Igneous Rocks
Sub-Class
Durable Rock, Soft Rock
Durable Rock, Medium Hardness Rock
Family
Group
-
Volcanic
Other Categories
Fine Grained Rock, Opaque Rock
Opaque Rock