What are the three main rock types?

• A. Igneous, sedimentary, and metamorphic.
• B. Granite, basalt, pumice.
• C. Sand, silt, clay.
• D. Metals, minerals, compounds.

Answer: (A)

Rocks are categorized by how they form into three broad types: igneous, sedimentary, and metamorphic. Igneous rocks come from molten material that cools and solidifies, either underground as intrusive rocks like granite or on the surface as lava that hardens into rocks such as basalt or pumice. Sedimentary rocks form from weathered and eroded material that is deposited, compacted, and cemented over time, often in layered beds and sometimes containing fossils, like sandstone or limestone. Metamorphic rocks arise when existing rocks are transformed by heat and pressure, changing mineral makeup and texture, as with slate from shale or marble from limestone. So the three main rock types are the names used to describe these formation processes. The other options mix specific rocks, grain sizes, or unrelated substances, which don’t give the broad classification of rocks.