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Which type of rock that will have small crystals if cooled rapidly?
== == The crystals will be small or may not form at all. Fast cooling magma produces small crystals. Slow cooling magma produces larger crystals. The longer a mineral has to form at its crystal growing temperature range, the larger the crystals will be.
Is pumice rock vesicular and glassy?
Yes. Pumice is so fine-grained, often times it's crystals are vesicular and glassy.
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.
What type of rock is formed from molten lava?
When molten magma cools and crystallizes, it becomes a hard rock called igneous rock. Different magmas have different compositions and so produce different igneous rocks. If the magma cools beneath the earth's surface, it cools slowly. Rocks formed like this are called intrusive rocks, and have large crystals, e.g. granite, gabbro, dolerite. If magma comes to the surface (in a volcanic eruption) it cools rapidly. Rocks formed like this are called extrusive rocks, and they have small crystals, e.g. basalt, obsidian, pumice. Igneous rocks have interlocking mineral crystals. The crystals are arranged randomly throughout the rock. Igneous rocks are mostly non-porous.
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?
== == The crystals will be small or may not form at all. Fast cooling magma produces small crystals. Slow cooling magma produces larger crystals. The longer a mineral has to form at its crystal growing temperature range, the larger the crystals will be.
Why are mineral crystals in obsidian too small to see without a microscope?
The rock cools so rapidly from magma that crystals barely have time to form.
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.
Is pumice rock vesicular and glassy?
Yes. Pumice is so fine-grained, often times it's crystals are vesicular and glassy.
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.
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.
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.
What crystal shape does obsidian have?
Quartz belongs to the hexagonal crystal system.
Do rocks have crystals?
Some rocks may contain crystals, but not all rocks contain crystals. Crystals can be found in rocks that have volcanic origin.
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.
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.
Why does obsidian rock contain no crystals?
obsidian doesnt crystalize because it was formed under water.
