Note:  Do not rely on this information. It is very old.

Primary Rocks

Primary Rocks, a term formerly applied in geology either to the plutonic igneous rocks (q.v.), such as granite, under the belief that they were the first rocks to form on the cooling of the earth from its primitively molten condition, or to the Palseozoic rocks (q.v.), as opposed to the Secondary and Tertiary. Being thus hopelessly ambiguous, it is now generally disused.