How Geologists Classify Rocks

Geologist classify according to TEXTURE Texture is the look and feel of a rock’s surface. Texture can be described as fine grained – with small particles Coarse grained – with large particles Glassy – no visible grain

Geologists classify according to Origin Igneous – forms from cooled magma or lava Sedimentary –forms from particles of other rocks or the remains of plants and animals that have compacted and cemented. Metamorphic – forms from rock that has been changed due to heat and pressure deep below earth’s crust.

IGNEOUS Igneous – forms from cooled magma or lava

Sedimentary forms from particles of other rocks or the remains of plants and animals that have compacted and cemented.

Metamorphic – forms from rock that has been changed due to heat and pressure deep below earth’s crust.

Geologists classify rocks according to Mineral composition Microscopes can be used to see crystal shape and structure Acid test can be used to test for carbonates Magnet test can be used to test for iron or nickel