Obsidian Stone

Obsidian

Obsidian is a naturally occurring volcanic glass formed when lava extruded from a volcano cools rapidly with minimal crystal growth. It is an igneous rock. Produced from felsic lava, obsidian is rich in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. It is commonly found within the margins of rhyolitic lava flows known as obsidian flows. These flows have a high content of silica, giving them a high viscosity. The high viscosity inhibits the diffusion of atoms through the lava, which inhibits the first step (nucleation) in the formation of mineral crystals. Together with rapid cooling, this results in a natural glass forming from the lava.

Rock (geology)

In geology, a rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its chemical composition, and the way in which it is formed. Rocks form the Earth's outer solid layer, the crust, and most of its interior, except for the liquid outer core and pockets of magma in the asthenosphere. The study of rocks involves multiple subdisciplines of geology, including petrology and mineralogy. It may be limited to rocks found on Earth, or it may include planetary geology that studies the rocks of other celestial objects.

obsidian

Noun

1. A type of naturally occurring black glass produced by volcanoes.
2. A slightly bluish black, the color of obsidian glass.

Adjective

1. Black.

stone

Noun

1. A hard earthen substance that can form rocks; especially, such substance when regarded as a building material.
2. A piece of such material: a block of stone, rock or a pebble.

Adjective

1. Constructed of stone.
2. Having the appearance of stone.