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
Marl is an unconsolidated sedimentary rock consisting of clay and lime
History
Origin
Ethiopia
-
Discoverer
Obsius
William Smith
Etymology
From Latin obsidianus, misprint of Obsianus (lapis) (stone) of Obsius
From Old French marle, from Late Latin marglia
Class
Igneous Rocks
Sedimentary Rocks
Sub-Class
Durable Rock, Medium Hardness Rock
Durable Rock, Soft Rock
Family
Group
Volcanic
-
Other Categories
Opaque Rock
Fine Grained Rock, Opaque Rock