Obsidian is available in nature as volcanic glass created as an igneous rock of extrusive nature. It gets created under circumstances where volcano extruding as felsic, cools rapidly with just a little crystal growth. You find this mineral mostly in hyolitic lava margins, also called obsidian flows.
The high silica content’s strong chemical configuration induces high temperature, leading to highly viscous polymerization of the lava that prevents excess crystal growth. The reservation of atomic diffusion through this exceedingly glutinous and polymerized lava explains the lack of crystal development. Obsidian has hard and brittle futures.
Plus MgO, Fe3O4
Derivation of Name
Elder Pliny’s translation of Natural History illustrates sufficiently about a volcanic glass they called Obsian, which name it owes to an Ethiopian stone discovered by Obsius.
Occurrence and Source
Obsidian gets formed in locations which have undergone rhyolitic eruptions. It is found in Argentina, Azerbaijan, Armenia, Canada, Chile, Greece, Georgia, Guatemala, Iceland, El Salvador, Italy, Japan, Mexico, Kenya, Scotland, Turkey, New Zealand, Peru, and the United States. Yellowstone National Park has a ridge, situated between Mammoth Hot Springs and the Norris Geyser Basin, containing obsidian.
Obsidian is used as a gemstone and for ornamental applications. It provides a different look, depending on how it is cut: in one direction it is jet black, while in another it is glossy gray. "Apache tears" are tiny round obsidian chunks implanted within a grayish-white perlite (amorphous volcanic glass) matrix.
Though mineral-like, obsidian is not an exact mineral because, being glass, does not give it a crystalline antecedence. Additionally, it has too many complex issues for it to be judged as a singular mineral. At times the experts classify it as a Mineraloid. Obsidian mostly comprises about 70% of SiO2 (silicon dioxide).
Deep black or blackish green.
Mohs scale hardness