Why do you think identifying the kinds of mineral found in a rock matter?
Answers
Igneous rocks
Igneous rocks have many distinct characteristics. For example, light-colored igneous rocks are more acidic, and have over 65% silica. Dark-colored rocks are more basic and have a higher percentage of ferro-magnesian minerals. Igneous rocks are broken up into three main groups: acid, intermediate, and basic. Acid rocks have over 65% silica, intermediate rocks have 55-65% silica, and basic rocks have 45-55% silica.
Igneous rock forms when magma (molten rock) cools and solidifies. Extrusive igneous rocks are those formed when magma reaches the surface (at which point it is called lava), cooling and solidifying quickly. Intrusive igneous rocks are formed when magma slowly cools deep below the surface of the earth. Different sized grains form, depending on the conditions of the rock formation. Intrusive rocks are generally more coarse-grained than extrusive. Coarse grains are more than 3/16 of an inch; medium grains, 1/64-3/16; and fine grains, less than 1/64 of an inch. Granite, Rhyolite, Obsidian, Diorite, Felsite, Basalt, and Pumice are all examples of igneous rocks. All these characteristics are key in identifying igneous rocks.