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Which type of rock that will have small crystals if cooled rapidly?
Igneous rocks will have small crystals if they cool rapidly. This is because rapid cooling does not allow enough time for large crystals to form. Examples of igneous rocks that exhibit small crystals due to rapid cooling include basalt and obsidian.
What does quick cooling of ejected lava result in?
Quick cooling of ejected lava results in the formation of glassy volcanic rocks, such as obsidian or pumice. These rocks are formed when the lava solidifies so rapidly that crystals do not have time to form within the rock. The resulting texture is usually smooth and non-crystalline.
What texture of obsidian?
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.
Is pumice rock vesicular and glassy?
Yes. Pumice is so fine-grained, often times it's crystals are vesicular and glassy.
What is a type of crystal grain that forms when rock cools Slowly?
When molten rock cools slowly, it will have a lot of time to form crystals, so the crystal size will be quite big. Take granite, for example. With the naked eye, you can see the individual crystals. The grain size is quite large. The kind of mineral that forms is dependent on the composition of the magma.
Which type of rock that will have small crystals if cooled rapidly?
Igneous rocks will have small crystals if they cool rapidly. This is because rapid cooling does not allow enough time for large crystals to form. Examples of igneous rocks that exhibit small crystals due to rapid cooling include basalt and obsidian.
Do all extrusive igneous rocks contain crystals?
No, not all extrusive igneous rocks contain visible crystals. Some extrusive rocks, such as obsidian and pumice, cool so quickly that mineral crystals do not have a chance to form, resulting in a glassy texture instead.
Why are mineral crystals in obsidian too small to see without a microscope?
Obsidian cools rapidly, preventing large crystals from forming. As a result, the mineral crystals are too small to be seen with the naked eye. The rapid cooling process hinders the growth of crystals, resulting in a smooth and glassy texture.
How does obsidian get its unusual texture?
The texture of a rock depends on the rate that it cools. Obsidian cools so quickly that no crystals can form, therefore giving it a glassy texture.
Did obsidian cool quickly or slowly?
Obsidian cooled very quickly. It's a vulcanic glass, meaning that the crystals are so small, they had virtually no time to form an orderly crystalline texture, and are basically placed randomly. Smaller grain size is associated with faster cooling.
Why do some igneous rocks have large crystals while others have small crystals or no crystals?
Mostly, it depends on cooling time. If a rock cools very rapidly, a smooth texture is formed as the atoms quickly arrange themselves into a fairly smooth crystalline pattern. Think of obsidian; it cools very fast and has such small crystals looks like black warped glass. However, if a rock was formed below the Earth's surface (intrusively) like in a pluton, it will cool more slowly and will be rougher and have larger crystals.
What does quick cooling of ejected lava result in?
Quick cooling of ejected lava results in the formation of glassy volcanic rocks, such as obsidian or pumice. These rocks are formed when the lava solidifies so rapidly that crystals do not have time to form within the rock. The resulting texture is usually smooth and non-crystalline.
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 texture of obsidian?
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.
Is obsidian a mineral?
No. Obsidian is not crystalline so is not a mineral. It forms from the extremely rapid cooling of lava which means that crystals do not have time to form. This is described as a vitreous or glassy texture.
Why does obsidian rock contain no crystals?
Obsidian forms when lava cools very quickly, preventing the formation of crystals. This rapid cooling doesn't allow enough time for the minerals in the lava to organize into a crystal lattice structure, resulting in a glassy texture instead.
How does the texture of gabbro compare to obsidian?
Both are made from volcanic rock. Pumice forms when lava cools very quickly and still has pockets of air trapped inside. This make the rock very lightweight and porous -- it can even float on water! Obsidian also forms when lava is quickly cooled, but it does not have trapped air pockets inside. It looks like glass and is rather brittle, but makes an excellent material for sharp cutting implements.
