welcome to moomoomath and science in this video let's take a look at the different types of rocks rocks are all around us they make up this famous formation called Half Dome or the smaller rock formation they can be small or seen in these canyons a rock is a 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 a 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 and then the extrusive igneous rocks so up first let's take a look at obsidian obsidian is a igneous extrusive or volcanic rock it's made up of quartz alkali and feldspar it looks a little bit like glass and as a hardness between 6 and 7 so there's obsidian next we have granite granite is an igneous intrusion ik Rock it's made up of filled spar quartz and mica it has medium to coarse grain crystals and a hardness between 5 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-grained and it has a 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 filled spar quartz and mica it has a very fine texture and often it has a 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 a 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 formed by precipitation of minerals from water precipitation is when dissolved minerals come out of water in organic sedimentary rocks such as coal and limestone which formed 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 shell shell is a fine-grained clastic sedimentary rock composed of mud this mud is a mix of flakes of clay minerals and silt size 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 a 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 a 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 lime stones metamorphic rocks come from existing rocks that are subjected to extreme heat and pressure this heat and pressure changes the original structure into a 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 a 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 find the medium crystals its parent rock is limestone and it's considered non-foliated quartzite our is a non-foliated metamorphic rock and its parent rock is sandstone nice is a foliated rock and its parent rock is schist and finally schist is a 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 moomoomath 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