Small crystal grains form from rapid cooling of magma resulting in an aphanitic rock texture.
Fine
fine
lava
Pumice is made of glass. Glass forms when molten rock cools too quickly for crystals to form.
it forms ingenous rock ...
When molten rock cools quickly, fine-grained crystals form. This happens because there is not enough time for larger crystals to grow before the rock solidifies, resulting in smaller crystals being formed.
Obsidian forms when molten lava cools quickly upon contact with cold water.
When molten material reaches the surface of the Earth, it can solidify into different forms depending on the speed of cooling. If it cools quickly, it forms extrusive igneous rocks like basalt. If it cools slowly underground, it forms intrusive igneous rocks like granite.
There are three types of rock - igneous, sedimentary and metamorphic. Igneous rocks formed directly from magma (molten rock flowing under ground) or lava (molten rock flowing above the crust). Granite is an example of what forms as magma cools slowly over a very long time, and obsidian forms when lava cools quickly, such as from contact with ocean water.
Igneous
When melted rock cools, it forms igneous rock. The process of cooling allows the molten rock, also known as magma or lava, to solidify and form crystals. Igneous rocks can have different textures and compositions depending on how quickly or slowly the rock cools.
Igneous rock