There are three general categories of rocks: igneous, sedimentary, and metamorphic.
Igneous rocks include granite, basalt, and obsidian. They are formed by the solidification of liquid magma or lava
Sandstone, limestone, and shale are sedimentary rocks created by accumulation and lithification.
Marble, slate, and gneiss are metamorphic rocks. They have changed mineral composition, texture, or both as a result of high temperature, high pressure, or both, but not by melting.