Why is obsidian glassy and smooth?

Obsidian is natural glass that was originally molten magma associated with a volcano. This volcanic glass has an almost total absence of sizable mineral crystals within the glass matrix. This smooth, curved type of fracture surface occurs because of the near-absence of mineral crystals in the glass.

Why does obsidian have a glassy texture?

Very quickly cooled lavas, typically those quenched in water, will have a glassy texture. They cool too quickly to form crystals. Glasses do not have an orderly arrangement of atoms and there are therefore no minerals, in the strict sense, in them. Volcanic glass is called obsidian.

Why is obsidian dark and glassy?

Pure obsidian is usually dark in appearance, though the color varies depending on the impurities present. Iron and other transition elements may give the obsidian a dark brown to black color. Most black obsidians contain nanoinclusions of magnetite, an iron oxide. Very few samples of obsidian are nearly colorless.

How does a rock become glassy?

When lava comes out of a volcano and solidifies into extrusive igneous rock, also called volcanic, the rock cools very quickly. If lava cools almost instantly, the rocks that form are glassy with no individual crystals, like obsidian.

Is obsidian translucent?

Transparency: Obsidian is translucent in any stone of appreciable size. Crystal System does not apply because obsidian is amorphous . Best Field Indicators are color, fracture, flow bubbles, softness, association with other volcanic rocks and lack of crystal faces.

Why is obsidian dark in color?

Obsidian is commonly a translucent dark brown or black. Unlike basalt, obsidian’s dark color is due to high amounts of impurities rather than the presence of dark colored minerals. The color of obsidian depends on the chemical composition of the impurities.

What is glassy rocks?

If a rock looks like a block of (colored) glass, with no visible mineral crystals, it has a glassy texture. Superficially, a glassy texture suggests cooling that was so extremely fast that no crystals could form.

What type of rock has a glassy texture?

Obsidian
Obsidian is the common rock that has a glassy texture, and is essentially volcanic glass. Obsidian is usually black.

What is the texture of obsidian?

Glassy
Obsidian

What kind of rock is obsidian?

igneous rock
Rondi: Everyone, meet Obsidian , an igneous rock that from melted rock, or magma. Obsidian is an “extrusive” rock, which means it is made from magma that erupted out of a volcano.