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An igneous rock has two different textures. Extrusive rocks generally are smooth and glassy. Intrusive rocks are generally coarse
A glassy texture.
Obsidian is an extrusive rock that cooled very rapidly without forming crystals. As a result, obsidian has a smooth, shiny texture of a thick piece of glass.
No, igneous rocks are not classified by their shape. They are primarily classified based on their origin (either intrusive or extrusive) and their texture (coarse-grained, fine-grained, glassy, etc.). Shape or form is not a major factor in the classification of igneous rocks.
The main difference is that the glassy textured igneous rock cooled from lava with extreme quickness, while the one with a fine texture cooled less quickly. Obsidian is a natural glass, created by rapidly cooling lava, where mineral crystals do not have enough time to form before the lava solidifies.
basalt
Obsidian
An igneous rock with a glassy texture cooled from its' liquid state very quickly, an example of this would be obsidian, a volcanic glass.
Obsidian is an igneous rock with a glassy texture. Its texture is also called hyaline, the Greek word for texture.
Basaltic glass
glassy texture
It pretty much forms from no crystallization. ;)
Granite is a coarse grained igneous rock without Pyroxene.
A vesicular igneous texture generally indicates rapid cooling.
An igneous rock has two different textures. Extrusive rocks generally are smooth and glassy. Intrusive rocks are generally coarse
glassy texture, hope this helps :)