1. Extrusive (Volcanic): These rocks form from the cooling and solidification of lava on the Earth's surface. They tend to have fine-grained textures due to rapid cooling. Examples include basalt, rhyolite, and andesite.

2. Intrusive (Plutonic): These rocks form from the cooling and solidification of magma beneath the Earth's surface. They generally have coarse-grained textures due to slow cooling. Examples include granite, gabbro, and diorite.

3. Ultramafic: These rocks are a special category of intrusive rocks characterized by their high magnesium and iron content. They are typically very dark in color and are often found in the Earth's mantle. Examples include peridotite and dunite.