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Some igneous rocks are very smooth and glassy (obsidian) while others have a very rough texture, such as the rocks used on the bottom of a propane gas grill.
They are all formed from lava, but the glassy rocks cooled so fast that crystals did not have a chance to form. The rougher rocks cooled more slowly, allowing larger crystals to form--Slower cooling = larger crystals = rougher texture.
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∙ 14y ago
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∙ 9y agoobsidian
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What characteristics determines the chemical composition of an igneous rock?
An igneous rock is any crystalline or glassy rock that forms from cooling of a magma. Color and texture help determine the chemical composition of the rock.
What type of rock is formed when an igneous rock is cooled very rapidly?
When magma is cooled, it forms an igneous rock. When magma is cooled rapidly, that igneous rock is of the category called "extrusive" or "volcanic". When the magma is cooled very rapidly, the extrusive igneous rock formed will probably be holohyaline (glassy) in texture, or foamy like pumice.However if you take an igneous rock that is already rock and cool that very rapidly it will probably shatter owing to thermal stress. That might result in the formation of tuff.
Is obsidian a sedimentary rock igneous rock or a metamorphic rock?
obsidian is an igneous rock, it is not formed from sediment, or a rock going under heat and pressure for the second time it is formed when a volcano erupts and it cools very quickly giving it a smooth glossy surface like glass.
What describes rock that was formed when molten rock cooled down?
Igneous rock is formed.
When Magma is launched from a volcano forms what type of rock?
A volcano is made of extrusive igneous rock. The specific type of igneous rock will vary from one volcano to another.
What is a smooth glassy black igneous rock?
Volcanic glass or obsidian.
What is the luster of igneous rock?
i think that igneous and metamorphic rocks uses luster because maybe they have it in them
What is the texture of Intrusive igneous rocks?
An igneous rock has two different textures. Extrusive rocks generally are smooth and glassy. Intrusive rocks are generally coarse
How do Igneous rock with glassy textures?
An igneous rock with a glassy texture cooled from its' liquid state very quickly, an example of this would be obsidian, a volcanic glass.
Why does pumice have a lower density than other igneous rocks?
It is a glassy igneous rock, so there are holes in it. The holes make the rock less dense than other igneous rocks that are Not glassy.
What rock is black glassy and was formed by rapidly cooling lava?
The answer is pitchstone. it is and igneous rock.
What are characteristics of basaltic igneous rock?
mainly glassy with amygdules and glass
What igneous rock has no visible crystals?
Granite is a coarse grained igneous rock without Pyroxene.
What is the name of a smooth glassy black ingeous rock?
Obsidian
Is granite a glassy igneous rock?
Granite is not metamorphic, but an intrusive igneous rock formed from cooling magma.
Which igneous rocks would be formed by the fastest cooling of lava?
Glassy textured extrusive igneous rock, such as obsidian.
A smooth glassy black igneous rock?
Yes. Obsidian is shiny on unweathered fracture surfaces. It is also an extrusive rock that is felsic, and can be worked to nearly molecular thinness at the edges.
