There isn't a strict classification of igneous rocks into just four types. However, you can broadly categorize igneous rocks based on their mineral composition and texture, which are determined by their cooling history. Here are four categories that cover most igneous rocks:

1. Felsic Rocks:

* Mineral Composition: Rich in silica (SiO2), with high proportions of feldspar and quartz.

* Texture: Often light-colored, with a fine-grained texture (like granite) or a glassy texture (like obsidian).

* Examples: Granite, rhyolite, obsidian.

2. Intermediate Rocks:

* Mineral Composition: Moderate silica content, with a mix of feldspar, quartz, and mafic minerals (like pyroxene and amphibole).

* Texture: Typically grey or light-colored, with a medium-grained texture (like diorite) or a fine-grained texture (like andesite).

* Examples: Diorite, andesite.

3. Mafic Rocks:

* Mineral Composition: Relatively low silica content, with high proportions of mafic minerals (like pyroxene and olivine).

* Texture: Dark-colored, with a coarse-grained texture (like gabbro) or a fine-grained texture (like basalt).

* Examples: Gabbro, basalt.

4. Ultramafic Rocks:

* Mineral Composition: Extremely low silica content, composed primarily of mafic minerals (like olivine and pyroxene).

* Texture: Very dark colored, with a coarse-grained texture.

* Examples: Peridotite, dunite.

Additional Notes:

* This classification is a simplification, and many other igneous rocks exist, with variations in composition and texture.

* The names of igneous rocks are determined by their chemical composition and their texture.

* The texture of igneous rocks (fine-grained, coarse-grained, glassy, etc.) depends on how quickly the magma or lava cooled.