Types of Rocks Igneous Sedimentary Metamorphic Rocks

Welcome to Moomeu Math and Science. In this video, let's take look at the different types of rocks. Rocks are all around us. They make up this famous formation called Half Dome or this smaller rock formation. They can be small or seen in these canyons. rock is solid naturally occurring and is made up of minerals or mineral-like matter like shells. Rocks can be divided into three basic types depending on how they are formed. These types are igneous sedimentary and metamorphic. Let's take look at these different types of rocks. Igneous rocks are formed when magma or molten rock cools. This magma can either flow to the surface of the earth and cool quickly and these rocks are called extrusive or volcanic igneous rocks and they generally have very small crystals. Or they can cool inside the earth and these are called intrusive or plutonic rocks and they generally have larger crystals than the extrusive igneous rocks. So up first, let's take look at obsidian. Obsidian is igneous extrusive or volcanic rock. It's made up of quartz, alkali and feldspar. It looks little bit like glass and it has hardness between six and seven. So there's obsidian. Next, we have granite. Granite is an igneous intrusive or plutonic rock. It's made up of feldspar, quartz and mica. It has medium to coarse grain crystals and hardness between five and 5.5. Next is basalt. It's an igneous extrusive rock. It is made up of plagioclase feldspar and pyroxene. It is dark and dense and is very fine grain. And has hardness between five and six. So there's basalt. Next, we have scoria. It's an igneous volcanic rock. It's made from feldspar augite and also hornblende. It is basalt with cavities filled with other minerals. And finally, we have rhyolite. It's an igneous extrusive rock. It's made from feldspar quartz and mica. It has very fine texture and often it has porous texture and it can float in water. So there we go, five igneous rocks. Sedimentary rocks are formed from pre-existing rocks or pieces of once living organisms. They form from deposits that accumulate on the earth's surface or under the ocean. These particles that form sedimentary rock are called sediment and may be composed of minerals or once living matter called organic matter. Sedimentary rocks can be divided into several groups. Some common groups include clastic sedimentary rocks which form from fragments of pre-existing rocks chemical sedimentary rocks which form by precipitation of minerals from water. Precipitation is when dissolved minerals come out of water. And organic sedimentary rocks such as coal and limestone which form from the accumulation of plant and animal debris. Clastic sedimentary rocks are subdividing according to the dominant particle size. These particle sizes are ranked from smallest to largest. Clay is the smallest, then silt sand, gravel, pebble and boulder. Up first, shale. Shale is fine grain clastic sedimentary rock composed of mud. This mud is mix of flakes of clay minerals and silt-sized particles of other minerals, especially quartz and calcite. Shale is very fine grain. Next, let's look at sandstone. Sandstone is one of the most common types of sedimentary rock found throughout the world. It is clastic sedimentary rock composed of sand-sized grains of mineral rock or even organic material. It also contains some cementing material that binds the sand grains together. Next, conglomerate. Conglomerate is coarse grain clastic sedimentary rock composed of pebbles and boulders. The space between these pebbles and boulders is generally filled with smaller particles of calcite or quartz cement that binds the rock together. And finally, limestone. Limestone is an organic sedimentary rock that is often composed of the skeleton fragments of marine organisms such as coral. About 10% of sedimentary rocks found on earth are limestones. Metamorphic rocks come from existing rocks that are subjected to extreme heat and pressure. This heat and pressure changes the original structure into new type of rock. Sedimentary, igneous and even metamorphic rocks can all become metamorphic rocks when exposed to heat and pressure. The original rock is the protolith but is commonly referred to as the parent rock. Metamorphic rocks can form deep in the earth's crust or areas of plate tectonic movement. Two major types of metamorphic rocks are foliated rocks which have crystals in stripes and non-foliated which do not have crystals in stripes. So let's take look at some common metamorphic rocks. Slate. It has very, very small minerals. It is considered foliated and its parent rock is shale. Marble has fine to medium crystals. Its parent rock is limestone and it's considered non-foliated. Quartzite or is non-foliated metamorphic rock and its parent rock is sandstone. Gneiss is foliated rock and its parent rock is schist. And finally, schist is foliated metamorphic rock and its parent rock is slate. If you need to know more about metamorphic rocks, this playlist should help. And as always, thanks for watching and Moomeu Math uploads new math and science video every day. Please subscribe and share.