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Obsidian volcanic glass formed by quenching of magma.
It is typically black, smooth and has a glassy to vitreous luster.
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∙ 15y ago
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A rock with large crystals surrounded by small crystals is called?
porphyry
How do small crystals form?
Answer: Crystals usually form from molten rock as the molten rock gradually cools. If the molten rock cools very rapidly, then either small crystals form or no crystals form. An example of this is when lava is ejected from a volcano. If molten rock cools slowly, then large crystals can form. This happens usually when the molten material is very deep in the Earth. Examples of these types of crystals are diamonds, emeralds, rubies, etc.
Shape of basalt?
Basalt is a rock, not a mineral, and therefore does not have a crystal structure of it's own.
A rock with large crystals surrounded by small crystals called?
It's an igneous porphyry.
Describe and explain the difference in the crystalline texture of volcanic rock and rock formed from an intrusion?
The texture of intrusive igneous rocks is phaneritic, which is characterized by coarse-grained large crystals that are visible to the naked eye. The texture of volcanic rocks, meanwhile, is porphyritic, which is characterized by fine-grained crystals.
What is a black intrusive rock with small crystals?
Intrusive rock normally has visible crystals. Extrusive igneous rock has small crystals. A black extrusive igneous rock with small crystals could be basalt.
Why do plutonic rock and volcanic rock have big and small crystals respectively?
The size of the crystals is a function of the rate of cooling of the molten rock. The faster the molten rock cools, the smaller the crystals will be.
Is shale a volcanic rock with small crystals made when lava cools?
No. Shale is a sedimentary rock formed from mud.
Why do plastic rock and volcanic rock have big and small crystals respectively?
Plutonic rock tends to have large crystals because it solidifies deep underground, where the overlying material insulates it so that it cools slowly, allowing time for large crystals to form. Volcanic rock tends to have small crystals (or to be amorphous) because it solidifies above ground, where air and water can cool it quickly by convection. Rapid cooling does not allow time for crystals to grow large. Plastic rock I don't know about.
What causes volcanic rock to have no crystals?
rapid cooling, so that crystals do not form.
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.
Must all rocks form crystals?
All rock does not contain mineral crystals. Obsidian, or volcanic glass, in particular is a rock that has cooled so quickly from lava that mineral crystals were not able to form.
What igneous rock cooled the most rapidly?
Igneous rocks with very small or no visible crystals are formed by rapid cooling. A good example would be obsidian (which is a volcanic glass) and BAsalt which may have an aphanitic texture (crystals to small to see with the naked eye).
A rock with large crystals surrounded by small crystals is called?
porphyry
How do small crystals form?
Answer: Crystals usually form from molten rock as the molten rock gradually cools. If the molten rock cools very rapidly, then either small crystals form or no crystals form. An example of this is when lava is ejected from a volcano. If molten rock cools slowly, then large crystals can form. This happens usually when the molten material is very deep in the Earth. Examples of these types of crystals are diamonds, emeralds, rubies, etc.
Hollow rock with crystals called?
A hollow rock with crystals might be called a geode. A geode is a type of sedimentary rock that has crystals formed inside due to volcanic heating and cooling or by other chemicals seeping into the rock.
Why do andesite have small crystals?
Andesite is an Igneous Rock. It has small crystals because it cooled quickly d;D
