Formation of Metamorphic Rocks
Metamorphic rocks are rocks that initially start their formation processes as sedimentary rocks which were slowly formed by compression with the water being squeezed out and the rock granules bonding under the immense pressure of many layers of rock pushing down on them and causing them to be formed in the sedimentary way, or as igneous rocks which are ejected when crystallized and then subjected to heat and pressurisation as they become metamorphic. The increasing pressure of the rock layers pushes the partially formed rocks into the vicinity of magma, which partly obliterates the original structure. The minerals are chemically altered and the heat and pressure they are subjected to causes them to develop some crystals and morph into metamorphic rocks. The heat and pressure changes the rocks so they transform chemically, this is called metamorphism.
Structure of Metamorphic Rocks
Metamorphic rocks, due to their unusual formations, have unusual structures. They are constituted of the typical crystals present in igneous rocks, from their period underground, and also bands of sediment from the period where they were pressurised under riverbeds in the usual creation of sedimentary rocks. They will generally resemble a rock with many crystals arranged into layers, however there are many different categories as some metamorphic rocks are formed from igneous rocks (like slate, formed from shale) and some from sedimentary rocks (like marble, formed from limestone).
How do metamorphic rocks differ from other rocks?
Metamorphic rocks differ from other rocks seeing as they are formed through a completely different process and contain the characteristics of both rocks. Sedimentary rocks contain bands of granules and igneous rocks contain randomly arranged crystals, however metamorphic rocks contain crystals formed into layers. This can be useful for construction purposes as they layers of crystal can easily be separated, as with thin individual bands of slate being used as roof tiles. In general, metamorphic rocks are chemically different, seeing as their formation distorts their chemical properties and they are also physically different due to the orderly arrangement of their crystals.
Examples of Metamorphic Rocks
Marble: Marble is a metamorphic rock formed from limestone (sedimentary). It is predominantly white with bands of crystals and is used for decorative purposes and construction, as it is incredibly hard.
Slate: Slate is formed from shale (igneous). It is a grey, dull, relatively brittle rock that can easily be separated into layers and this property makes it excellent for making roof tiles.
Quartzite: An extremely hard metamorphic rock formed from sandstone (sedimentary) which is either white/grey or red (if iron oxides are present). Its orderly crystals make it attractive and it is used for decorations. Predominantly formed from quartz alongside some other materials.
Phyllite: Another metamorphic rock formed from shale, it has been subjected to a higher degree of pressure and heat than slate. It has larger crystals making it more reflective and attractive than slate.
Schist: Another rock formed from shale, with an even higher pressure/ heat application. It has even larger, flat elongated crystals (the constituent minerals have been pressed flat) and is formed when enough pressure is applied that mountains are created. It is present under Manhattan in large amounts and has highly visible crystals and layers. It is classified as coarse-grained.
Gneiss: Gneiss is a very common metamorphic rock which has been subjected to the highest amount of pressure. It is originally formed from shale, but due to the heat most of the minerals have recrystallized into dark and light bands of crystal. Gneiss is hard and considered an attractive rock.
Metamorphic rocks are rocks that initially start their formation processes as sedimentary rocks which were slowly formed by compression with the water being squeezed out and the rock granules bonding under the immense pressure of many layers of rock pushing down on them and causing them to be formed in the sedimentary way, or as igneous rocks which are ejected when crystallized and then subjected to heat and pressurisation as they become metamorphic. The increasing pressure of the rock layers pushes the partially formed rocks into the vicinity of magma, which partly obliterates the original structure. The minerals are chemically altered and the heat and pressure they are subjected to causes them to develop some crystals and morph into metamorphic rocks. The heat and pressure changes the rocks so they transform chemically, this is called metamorphism.
Structure of Metamorphic Rocks
Metamorphic rocks, due to their unusual formations, have unusual structures. They are constituted of the typical crystals present in igneous rocks, from their period underground, and also bands of sediment from the period where they were pressurised under riverbeds in the usual creation of sedimentary rocks. They will generally resemble a rock with many crystals arranged into layers, however there are many different categories as some metamorphic rocks are formed from igneous rocks (like slate, formed from shale) and some from sedimentary rocks (like marble, formed from limestone).
How do metamorphic rocks differ from other rocks?
Metamorphic rocks differ from other rocks seeing as they are formed through a completely different process and contain the characteristics of both rocks. Sedimentary rocks contain bands of granules and igneous rocks contain randomly arranged crystals, however metamorphic rocks contain crystals formed into layers. This can be useful for construction purposes as they layers of crystal can easily be separated, as with thin individual bands of slate being used as roof tiles. In general, metamorphic rocks are chemically different, seeing as their formation distorts their chemical properties and they are also physically different due to the orderly arrangement of their crystals.
Examples of Metamorphic Rocks
Marble: Marble is a metamorphic rock formed from limestone (sedimentary). It is predominantly white with bands of crystals and is used for decorative purposes and construction, as it is incredibly hard.
Slate: Slate is formed from shale (igneous). It is a grey, dull, relatively brittle rock that can easily be separated into layers and this property makes it excellent for making roof tiles.
Quartzite: An extremely hard metamorphic rock formed from sandstone (sedimentary) which is either white/grey or red (if iron oxides are present). Its orderly crystals make it attractive and it is used for decorations. Predominantly formed from quartz alongside some other materials.
Phyllite: Another metamorphic rock formed from shale, it has been subjected to a higher degree of pressure and heat than slate. It has larger crystals making it more reflective and attractive than slate.
Schist: Another rock formed from shale, with an even higher pressure/ heat application. It has even larger, flat elongated crystals (the constituent minerals have been pressed flat) and is formed when enough pressure is applied that mountains are created. It is present under Manhattan in large amounts and has highly visible crystals and layers. It is classified as coarse-grained.
Gneiss: Gneiss is a very common metamorphic rock which has been subjected to the highest amount of pressure. It is originally formed from shale, but due to the heat most of the minerals have recrystallized into dark and light bands of crystal. Gneiss is hard and considered an attractive rock.