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Rocks All rocks are combinations of minerals However, not all rocks are the same Rocks can be created in different ways and can be found in different places There are 3 main categories of rocks. IGNEOUS ROCKS The term igneous comes from the Latin word “ignis” which means “fire” Igneous rocks are formed from the hardening and crystallization of magma/lava So basically, an igneous rock is just cooled lava Examples of Igneous Rocks • • • Granite- often used because of its strength, durability and beauty Obsidian- used as knife blades, as well as in jewelry and sculptures Kimberlite- diamonds are often found inside kimberlite SEDIMENTARY ROCKS Sedimentary rocks are made of tiny bits of dirt, sand, minerals and other rocks These tiny bits of stuff are called sediments (hence the name!) Heat and pressure cause the sediments to cement (stick) together SEDIMENTARY ROCKS Fossils - Most fossils are found in sedimentary rock - When an organism (plant or animal) dies, it may get buried before it decomposes (rots) - Parts of the organisms can even be replaced by minerals and turned into rocks, such as fossilized shells Examples of Sedimentary Rocks Sandstone- as the name suggests, it is made of grains of sand; often oil is found beneath layers of sandstone Shale-also known as “mudstone”; usually found near slowly moving water Limestone- made of dead organisms and/or their shells; often found in shallow waters Coal- made from the carbon in dead plants; can be burned for energy METAMORPHIC ROCKS When rocks get buried deep enough in the ground, they can experience enough pressure and heat that they will change into something new (though if it is too deep it will just melt back down into magma) So, basically, a metamorphic rock is an old rock that has been baked into a new type of rock Examples of Metamorphic Rocks Schist- used to be shale Gneiss- used to be granite Marble- used to be limestone; often used in statues PRACTICE 1. Fossils are found in this type 2. Granite is an example of this type 1. Sedimentary 2. Igneous 3. Gneiss used to be granite and is this type 3. Metamorphic 4. Diamonds can be found sometimes in kimberlite which is an example of this type 4. Igneous 5. This type is made of tiny bits of stuff called sediments 5. Sedimentary 6. This type is old rock that is baked into new rock 7. This type is made from lava 6. Metamorphic 7. Igneous