94.8 CTS A GRADE RAINBOW OBSIDIUM SLAB [F5710 ]

Item Information

Dimensions (mm) 50 x 35 x 7mm
Weight (carats) 94.8 carats
Colors

QUALITY ROUGH

A GRADE OBSIDIUM SLAB

This is a piece we cut off a rough specimen at app 45 degree angle to expose the amazing patterns.Great cutting experience.We have taken the photo with the rough wet.

General
CategoryVolcanic glass
Formula (repeating unit)70–75% SiO2, plus MgO, Fe3O4
Identification
ColorDeep black or blackish green
FractureConchoidal
Mohs scale hardness5–6[1]
LusterVitreous
Specific gravity~2.4[2]
Optical propertiesTranslucent
References[3]

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. Obsidian is commonly found within the margins of rhyolitic lava flows known as obsidian flows, where the chemical composition (high silica content) induces a high viscosity and polymerization degree of the lava. The inhibition of atomic diffusion through this highly viscous and polymerized lava explains the lack of crystal growth. Obsidian is hard and brittle; it therefore fractures with very sharp edges, which were used in the past in cutting and piercing tools, and has been used experimentally as surgical scalpel blades. It may contain patterns of gas bubbles remaining from the lava flow, aligned along layers created as the molten rock was flowing before being cooled. These bubbles can produce interesting effects such as a golden sheen (sheen obsidian). An iridescent, rainbow-like sheen (rainbow obsidian) is caused by inclusions of magnetite nanoparticles

$29.00 USD

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Pricing & Details

Auction ID 492528
Watchers 5 watching
Viewed 1,151 times
Starts 21st Apr 2015 7:43pm PDT

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