how long they stayed in the volcano; how much time the crystals had to form
If you're not looking for anything specific, any extrusive igneous rock will have smaller crystals, if any at all. This is because they cool quickly on the surface, leaving little time for crystals to form/grow.
Extrusive Igneous Rocks. Basalt (Plankey1995 JF)
Small crystals, invisible without magnification.
Extrusive igneous rocks have very small crystal grains.
Yes. Igneous rock that forms on the surface will have small mineral crystals, or in some cases no mineral crystals. Igneous rock that forms below the surface will have larger mineral crystals, from the additional cooling time afforded by the insulating effects of the surrounding Earth material.
It depends on the type of igneous rock. Intrusive igneous rocks such as granite have large crystals, extrusive igneous rocks may have small crystals as in basalt or no crystals as in pumice.
you would find igneous rocks with small crystals at the bottom of the volcano, this is because when the rocks crack. It brakes apart into igneous rocks
Such rocks are called porphyritic.
Igneous rocks that cooled slowly are intrusive. Igneous rocks that cooled quickly are extrusive. Intrusive rocks form larger crystals, because the crystals have a longer time to grow. Extrusive rocks have small to no crystals, because they had little or no time to grow/form.
Some extrusive igneous rocks have individual mineral crystals that are too small to be seen without magnification.
If you're not looking for anything specific, any extrusive igneous rock will have smaller crystals, if any at all. This is because they cool quickly on the surface, leaving little time for crystals to form/grow.
That is correct.
Extrusive Igneous Rocks. Basalt (Plankey1995 JF)
These are extrusive igneous rocks with an aphanitic texture.
When igneous rocks cool quickly, they have small crystals and have a texture that may be described as aphanitic. When igneous rocks cool slowly, they have much larger crystals and have a texture that may be described as phaneritic or pegmatitic.
Yes, they can. Extrusive igneous rocks, which form outside the Earth's surface, often contain small or no crystals, because they cool quickly and the particles in the lava do not have much time to arrange themselves. Intrusive rocks, which form inside the Earth, generally have large crystals because they cool slowly. Granite is an example of an igneous rock with large crystals.
If lava cools quickly, the minerals don't have as much time to form crystals, so the crystals do not become very large. Igneous rocks that cooled quickly and have small crystals are described as "aphanitic" igneous rocks.