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Obsidian and Tachylite are extrusive felsic (high silica content > 69% SiO2) and mafic (low silica content < 52% SiO2) igneous rock types respectively.
They are commonly known as volcanic glasses and form due to the rapid cooling of lava. This rapid cooling prevents mineral crystallisation from occurring and this accounts for their "glassy" (or more correctly their vitreous)A texture.
A A vitreous material is an amorphous (i.e. non crystalline) solid material.
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What igneous rock has crystals that are not visible?
Extrusive igneous rock consists of mineral crystals that are not observable with the naked eye. Obsidian is an extrusive igneous rock (volcanic glass) where there technically are no mineral crystals.
Where does pumice form?
Vesicular solidified lava, an extrusive igneous rock.
What is a very light igneous rock honeycomed volcanic glass?
Pumice
What kind of igneous rock is obsidian?
Obsidian is an igneous rock. However it differs from other rocks because it contains no minerals. It consists of natural glass, which is not a mineral because it has no crystal structure.Answers from McDougal Littell, Earth Science book
What is the darkest igneous rock?
Obsidian is black volcanic glass, and is extremely dark.
Is volcanic glass an intrusive or extrusive igneous rock?
Volcanic material is extrusive.
What is the obsidian rock type?
Obsidian is an extrusive felsic igneous rock.
What igneous rock has crystals that are not visible?
Extrusive igneous rock consists of mineral crystals that are not observable with the naked eye. Obsidian is an extrusive igneous rock (volcanic glass) where there technically are no mineral crystals.
What type igneous is pumice intrusive small crystal or extrusive large crystal?
It is neither. Pumice is an extrusive highly vesicular igneous rock composed of volcanic glass and very tiny mineral crystals.
What type of rocks form when lava cools after a volcanic eruption?
Igneous Rock is formed when a volcano erupts and the the lava cools down to harden. Pumice Stone Extrusive Rocks Glass Rocks Hope this Helps :)
Where does pumice form?
Vesicular solidified lava, an extrusive igneous rock.
How is obisidian formed?
Obisidian is formed when resedue from an active volcanco is cooled rapidly. Obisidian is an extrusive igneous rock made of a glass like substance formed from naturally occuring volcanic glass.
Is obsidian extrusive rock?
No. Obsidian is volcanic glass. Glass is amorphous and thus noncrystalline.
What is a naturally occurring igneous rock more correctly called obsidian?
Obsidian is also called volcanic glass, an extrusive, largely non-crystalline, felsic igneous rock. Pumice is also a frothy form of obsidian.
What is category of igneous extrusive rock?
Some igneous extrusive rocks include obsidian, basalt, andesite, rhyolite, scoria, pumice, basaltic glass. If you want more, go to page 6 on the Earth Science Reference Tables at the related link.
Where is Obsidian?
Obsidian is a naturally occurring glass formed as an extrusive igneous rock
What is an extrusive igneous rock that is actually glass?
One type of glassy igneous rock is obsidian, which is black and glass-like. Any type of igneous rock that is glassy would be a extrusive rock, which means it was formed outside the earths crust and cooled quickly, making for a fine grain and small crystals. hope this helps
