Rocks and Minerals Notes
Rocks are made up of minerals.
Minerals are made up of elements- either one alone or two or more called compounds.
There are three main types of rocks.
Scientists classify them by how they form-or their environment of formation.
-Are formed when molten material cools.
If the material cools at or on the surface of the earth it is an extrusive igneous rock.
Extrusive igneous rocks are formed from the cooling of ash
or lava. These are volcanic.
If the material cools beneath the earth’s surface, it is an intrusive (in for inside) igneous rock.
Intrusive igneous rocks are formed from the cooling of
magma. These are called plutonic.
Environment of formation can be identified by these characteristics
-interlocking crystals
-glassy appearance
-air bubbles in the rock
Size of crystals tells where the rock formed (size depends on temp)
-*No crystals-glassy appearance forms quickly above the
Earth’s surface
-*Medium to large crystals- rock forms slowly beneath the
Earth’s surface