Golden obsidian, also called golden sheen obsidian or sheen obsidian is a stone contains patterns of gas bubbles, remaining from the lava flow, aligned along layers created as the molten rock was flowing before being cooled.
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These bubbles produce interesting effects look like a golden sheen.
Golden sheen obsidian
A naturally occurring volcanic glass formed as an extrusive igneous rock.
It is produced when felsic lava extruded from a volcano cools rapidly with minimal crystal growth.
It is commonly found within the margins of rhyolitic lava flows known as obsidian flows, where the chemical composition, high silica content causes a high viscosity which, upon rapid cooling, forms a natural glass from the lava.
The inhibition of atomic diffusion through this highly viscous lava explains the lack of crystal growth. The stone is hard, brittle, and amorphous, it therefore fractures with very sharp edges. In the past it was used to manufacture cutting and piercing tools and it has been used experimentally as surgical scalpel blades.
Gold obsidian. A mineral-like
Not a true mineral because as a glass it is not crystalline, in addition, its composition is too variable to be classified as a mineral. It is sometimes classified as a mineraloid.
Though golden obsidian is usually dark in color, similar to mafic rocks such as basalt, obsidian’s composition is extremely felsic. Obsidian consists mainly of SiO2, silicon dioxide, usually 70% or more. Crystalline rocks with obsidian’s composition include granite and rhyolite.
Because obsidian is metastable at the Earth’s surface, over time the glass becomes fine-grained mineral crystals, no obsidian has been found that is older than Cretaceous age. This breakdown of obsidian is accelerated by the presence of water.
Having a low water content when newly formed, typically less than 1% water by weight, obsidian becomes progressively hydrated when exposed to groundwater, forming perlite.
Golden obsidian sphere