Metamorphic Rocks
Understanding the key characteristics of metamorphic rocks.
- Created by: Caitlin
- Created on: 19-05-13 12:44
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- Metamorphic Rocks
- Foliated - minerals have a preferred alignment
- Slate
- Parent Rock - Shale
- Clay minerals, Muscovite, Mica, Chlorite, Quartz
- Fine grained <1mm
- Low Grade Metamorphism - Low Pressure and Temp
- Regional Metamorphism
- Grey, Purple, Green or Black in colour
- Slaty Cleavage
- Schist
- Parent Rock - Shale
- Medium Grained 1 - 5mm
- Silvery Sheen
- Mica crystals at 90 degrees to pressure - Schistocity
- Medium Grade Metamorphism - Medium Pressure and Temp
- Regional Metamorphism
- Muscovite and Biotite Mica, Quartz, Garnet, Kyanite
- Garnets often form Porphyroblasts
- Gneiss
- Parent Rock - Shale
- High Grade Metamorphism - Highest Pressure and Temp
- Regional Metamorphism
- Coarse Grained >5mm
- Gneissose Banding - segregation of light and dark minerals
- Biotite Mica, Quartz, K Feldspar, Silimanite, Mafic Minerals
- Slate
- Unfoliated - no platy minerals to align
- Quartzite
- Parent Rock - Orthoquartzite
- Quartz grains recrystalise
- Interlocking crystals formed
- Crystals are equidimensional = no foliation
- Granobalstic
- Sedimentary structure are destroyed
- Grey or White in colour
- Other minerals in original rock will change colour
- Contact or Regional Metamorphism
- Marble
- Parent Rock - Marble
- Calcite crystals grow
- Granoblastic
- Medium Graine 1 - 5mm
- Interlocking Calcite Crystals
- Pure Limestone results in White Marble
- Clay Minerals in Limestone results in green or red minerals
- Sand Grains present in Limestone results in Wollastonite
- Wollastonite - light green, pinkish, brown, red or yellow
- Contact or Regional Metamorphism
- Spotted Rock
- Contact Metamorphism
- No Pressure, High Temp = No Foliation
- Spots = only partially recrystallised rock
- Parent Rock - Slate or Shale
- Slate is the parent = Foliation or Relict Bedding
- Clay minerals, mica
- Poorly formed minerals mica, andalusite,graphite) in spots
- Slaty Cleavage is Slate is the parent rock
- Fine Grained <1mm
- Grey, Purple, Green or Black with Darker Spots
- Quartzite
- Foliated - minerals have a preferred alignment
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