To determine which igneous rock would contain the largest crystals, we need to consider the cooling rate of the magma/lava from which these rocks are formed. Slower cooling rates generally result in the formation of larger crystals, while faster cooling rates lead to the formation of smaller crystals or even glassy textures.
1. Granite (Option A) is an intrusive igneous rock that forms beneath the Earth's surface, where cooling is slow. Therefore, granite typically contains larger crystals compared to other igneous rocks.
2. Obsidian (Option B) is an extrusive igneous rock that cools rapidly at the Earth's surface or in shallow subsurface environments. Due to its rapid cooling, obsidian lacks crystals and instead has a glassy texture.
3. Pumice (Option C) is also an extrusive igneous rock that cools quickly. Pumice contains numerous gas bubbles trapped within its structure, resulting in a porous texture rather than large crystals.
4. Rhyolite (Option D) is an extrusive rock with a composition similar to granite but forms from a more rapid cooling process. As a result, rhyolite tends to have smaller crystals compared to granite.
Therefore, the correct answer is A) Granite, as it is an intrusive igneous rock formed from slow cooling magma, which allows for the growth of larger crystals.
