How are rocks and minerals formed General Discussion. The earth's crust changes and causes new rocks to form and old rocks to change. This happens when the plates bump together. A mineral comes from something that was never alive. It can be classified by a chemical formula. Other minerals were formed from living materials like animals or vegetables. These minerals are fuels and gasses. Minerals can become exposed by the natural weathering processes. Igneous - Igneous Rocks are formed from cooled magma. Magma is melted rock deep inside the earth. Magma on the crust is called molten lava. Sedimentary - Sedimentary rocks are formed as sediments are pushed together or cemented by the weight of the water and layers of sediment above it. This process of layers settling to the bottom happens over thousands and thousands of years. Metamorphic - Metamorphic rocks are made by extreme pressure and/or heat applied to sedimentary or igneous rocks that changes their minerals.   They are both pressed down It gets weathered. Is made from compacted (pressed down) sediments.   Heat and pressure change the minerals which were igneous or sedimentary Formed from cooled lava or magma   All are made of minerals. Both experience heat and pressure   Venn Diagram by Trent and Vincent Additional discussion. Rocks are natural combinations of 1, 2 or more minerals. They are nonliving solids that are found in nature. Marble was formed by linestone under great heat. Marble was used fur statues, and today is used for counter tops and floors. It is used in bathrooms a lot and it is very old. Chalk - Formed from the skeletons of time sea animals that are too small to see with the naked eye. Limestone was formed by broken shells and tiny sea cretures. It is solid white color with no other colors. It might look a little chalky. Diamonds are the hardest known mineral. Quartzite was formed by sandstone in great pressure and heat. It was slowly cooled and has a whitish crystal. Opal comes from the Romans. It is different colors. Turquois came from the aztecs 3,000 years ago. It is a bluegreen color. Sandstone was formed by grains of sand settling at the bottom of the ocean which got pressed together. Quatz with iron was formed by cooling slowly, but has purplish color whith white spots, or can be clear, brown or black. Granite - a rock that you cn find really easily. Obsidian is black, smooth, and a little sharp. Pumice is light, white and bumpy Petrified Wood has reddish or brown color which shows the age stripes. It often looks like wood. Tufa - forms when lime is deposited from water into a rock surfact in areas of low rainfall. Gravel is blueish gray and bumpy. Coal, also called Black Gold, is millions of years old. We burn it for fuel or heat. People have been mining coal since the middle ages. It is hard and brittle and black. Mold - a hollow left in a sediment after an organism dissolves. Imprint - a trace fossil of an organism, such as a footprint, preserved in rock. Cast - a fossil formed by sediments filling a mold.