Igneous Rock
The earth crust is made up of 95% of Igneous rock. Igneous Rocks are one of the three main rocks in the rock cycle. Igneous rocks can only be formed by the cooling of either lava or magma also know as molten rocks from a volcanic explosion that is then forced to the surface as lava or magma. When molten cools down or freezes it then becomes a crystal like solidified rock, creating an Igneous rock.When igneous rocks are found underground it's called intrusive, when found above ground it's called extrusive.
Five common Igneous Rocks
There are many different types of igneous rocks formed and crystallized by lava and magma.To identify the different types of igneous rock you look at the minerals, colours and texture of each rock .
5 common igneous rocks are: obsidian,pumice, rhyolite, andesite and basalt.
1.Obsidian
Obsidian is a sharp volcanic glass that contains no gas. The colours is black or dark brown color.The texture is usually sharp some obsidian have white to light grey crystallizing spots surrounded by black glass known as snowflake obsidian.
2.Pumice
Pumice is a grey volcanic glass rock, unlike obsidian its texture is full of gas bubble holes . It is light in weight and floats like a sponge on water.
3.Rhyolite
Rhyolite texture is a high-silica,fine grained igneous rock. The colours are grey,light brown,tan,pale yellow and pink.It is known that the minerals and chemicals of rhyolite are similar to granite.
4.Andesite
Andesite is a fine-grained igneous rock, midway in colour and minerals composition between rhyolite and basalt. The common texture is porphyritic rock with medium brown and sometimes shaded grey.
5.Basalt
Basalt is a rich in iron fine-grained igneous rock, The colour of basalt is black to brown. there are bubble gas within basalt igneous rock known as scoria.