Jake Matijevic (rock) consistent with feldspar, such as sodium, aluminum and potassium, and lower concentrations of magnesium, iron and nickel than other such rocks previously found on Mars. The mineral content and elemental abundance indicates "Jake M" rock may be a mugearite, a sodium rich oligoclase-bearing basaltic trachyandesite. Igneous rocks similar to the "Jake M" rock are well known but occur rarely on Earth. On Earth, such rocks form when magma, usually found in volcanoes, rises to the surface, cools and partially solidifies with certain chemical elements, while the warmer liquid magma portion becomes enriched with the left-behind elements. By remarkable coincidence, the
Igneous rock of a planet, surrounded by pre-existing rock (called country rock); the magma cools slowly and, as a result, these rocks are coarse-grained. The mineral grains in such rocks can generally be identified with the naked eye. Intrusive rocks can also be classified according to the shape and size of the intrusive body and its relation to the other formations into which it intrudes. Typical intrusive formations are batholiths, stocks, laccoliths, sills and dikes. When the magma solidifies within the earth's crust, it cools slowly forming coarse textured rocks, such as granite, gabbro, or diorite. The central cores of major mountain