Materials of the Earth

• Igneous rocks are formed by the cooling and hardening of magma
• magma is a molten material that is under the earth's surface
• an igneous rock is intrusive if magma cools and solidifies beneath the earth's surface
• an igneous rock is extrusive from lava which is magma that reached earth's surface
• sedimentary rocks are deposited at the bottom of the rivers, lakes and oceans
• metamorphic rocks are the hardest kind of rocks produced by hardening of igneous and sedimentary rocks
• granite, gabbro, diabase, diorite, pegmatite, peridotite are examples of intrusive igneous rocks
• pumice, obsidian, rhyolite, scoria and dacite are examples of extrusive igneous rocks
• limestone, sandstone, dolomite, siltstone, gypsum, rock salt, chalk, coal are examples of sedimentary rocks
• slate, gneiss, schist, and phyllite are examples of foliated metamorphic rocks
• marble, quartzite, skarn, hornfels, ignite, garnet are examples of non-foliated metamorphic rocks