Rock it
by Mimi Badu
What are Rocks?
Rocks are composed of minerals.they are classified by how they were formed(their origin). There are three types of rocks Igneous,Sedimentary and Metamorphic.
Igneous Rocks
- formed by cooling and crystallization of molten rocks.
- They are formed inside and outside volcanoes
- The main types are intrusive and extrusive.
Intrusive
- rocks that crystallize slowly inside the earth's crust.
- contains large crystals
- also known as platonic igneous rocks
Extrusive
- rocks that crystallize quickly at earth's surface.
- Normally contains small crystals
Sedimentary Rocks
- formed by cementing and compaction
- they are formed at or near the Earth's surface
- The main types are inorganic land- derived, chemically and organically.
Inorganic Land- Derived-
- Clastic (Fragmental)- made of different sized particles cemented together.
Chemically and/or Organic-
- Crystalline: deposited when chemical in seawater precipitate and fall to ocean bottom.
- Bioclastic: rocks formed by accumulation of plant and animal remains (fragment)---> containing shells or plant material
Metamorphic Rocks
- formed when other rocks are exposed to heat and/or pressure without melting (melting --> magma -->igneous)
- They are formed deep within earth.
- The main types of metamorphic rock is Foliation and Non- Foliation.
Foliation
- alignment of minerals in a metamorphic rock.
- Banding- type of foliation that is a wavy colored stripe. (ex. dark and light banding caused caused by density.)
Non- Foliation
- has no alignment of minerals
- no banding
Regional Metamorphic- large masses of rocks changed by deep burial within earth
Contact Metamorphism- chemical and physical change to a rock caused by nearby intrusion or extrusion or molten rock.
Selected Rocks!
Gabbro (Igneous Rocks)
- Gabbro formed is an intrusive rock forming inside a volcano.
- Gabbro has a texture of coarse and its crystal size varies from 1mm to 10mm.
- The rock is Non- vesicular
- Gabbro is a
- dark color,
- its density is high
- It's composition is (Fe,Mg)
- Mineral Percentage
- plagioclase feldspar is 30%
- pyroxene(green) is 52%
- Amphibole is 5%
Limestone (Sedimentary Rocks)
- Limestone is is a organically formed rock.
- Limestone's texture is either crystalline or bioclastic. The grain size microscopic to very coarse.
- The composition is Calcite.
- Limestone precipitates of biologic origin or cemented shell fragments.
Marble ( Metamorphic Rocks)
- The texture of the metamorphic rock is Non- foliated.
- The grain size is Fine to coarse.
- The composition is Calcite and/or dolomite.
- It is a regional or contact metamorphism.
- Metamorphism of limestone or dolostone.