Why Does Granite Have Bigger Crystals Than Basalt

This coarse grain makes granite a favorite of rock climbers.

Why does granite have bigger crystals than basalt.

Obsidian and granite are igneous rocks so called because they were formed from the molten magma of volcanoes. Granite is an intrusive rock that is formed when magma cools inside the crust. It depends on the type of igneous rock. Why does granite have a lower melting point than basalt.

Intrusive igneous rocks have cooled slowly from magma extrusive rocks have. This slow cooling gives time for crystals to grow making it more coarsely grained than an extrusive rock. Basalt rocks have fine grained crystals while gabbro is made up of much larger coarse grained pieces. If magma cools quickly for example when basalt lava erupts from a volcano then many crystals form very quickly and the resulting rock is fine grained with crystals usually less than 1mm in size.

The crystals in granite being intrusive in nature will be larger than those in basalt an extrusive igneous rock. Basalt on the other hand has a smooth texture from rapid cooling usually by water. Granite contains more water and minerals that melt at lower temperatures rocks that are rich in which 2 elements melt at higher temperatures than rocks that contain higher levels of silicon. Obsidian is not a genuine mineral or rock it is a natural glass that contains microscopic mineral crystals.

Like gabbro granite and diorite basalt is an igneous rock and is also the most abundant bedrock on earth including under the surface and within ocean basins. 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. Intrusive igneous rocks have cooled slowly from magma extrusive rocks have. The crystals in granite being intrusive in nature will be larger than those in basalt an extrusive igneous rock.

What s the most obvious difference between basalt and gabbro. Beyond that their similarities end.