There are 4 different types of rock; sedimentary, metamorphic, igneous intrusive, and igneous extrusive.

Sedimentary 

Sedimentary rocks are formed by small particles of sediment (think sand) coming together and being compacted over a long time. This can create a non-uniform, often layered rock. Common types of sedimentary rocks include limestone, sandstone, conglomerate, and chert. 

Metamorphic 

Metamorphic rocks are formed when other types of rock are subjected to high heat and pressure. This transforms them into something different over a long period of time. They are often squished, smeared out, and folded, creating interesting patterns. Common types of metamorphic rocks include gneiss, slate, quartzite, marble, and schist.

Igneous intrusive 

Igneous intrusive rocks are formed by magma cooling in the earth’s interior. The rocks cool slowly and large crystals form in them. They are often non-uniform with large crystals that are visible to the naked eye. Common types of igneous intrusive rocks are diorite, granite, pegmatite, and gabbro.

Igneous extrusive

Igneous extrusive rocks are formed by the cooling of lava on the earth’s surface. The rock cools quickly and forms lots of small crystals. They are often uniform with lots of small crystals that are not visible to the naked eye. Common types of igneous extrusive rocks include basalt, dacite, andesite, and obsidian.