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
Travertine is a mineral consisting of layered calcium carbonate formed by deposition from spring waters
History
Origin
Ethiopia
Italy
Discoverer
Obsius
Marcus Vitruvius Pollio
Etymology
From Latin obsidianus, misprint of Obsianus (lapis) (stone) of Obsius
From Italian travertino a kind of building stone, from Tiburs, adjective from Tibur (Tivoli), in Italy
Class
Igneous Rocks
Sedimentary Rocks
Sub-Class
Durable Rock, Medium Hardness Rock
Durable Rock, Medium Hardness Rock
Family
Group
Volcanic
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Other Categories
Opaque Rock
Fine Grained Rock, Opaque Rock