Schist and Porphyry
Definition
Definition
Schist is a medium grade metamorphic rock with medium to large, flat, sheet like grains in a preferred orientation
Porphyry is a reddish-brown to purple igneous rock containing large phenocrysts of various minerals embedded in a fine-grained matrix
History
Origin
Unknown
Egypt
Discoverer
Unknown
Unknown
Etymology
From French schiste, Greek skhistos i.e. split
From Old French porfire, from Italian porfiro and in some cases directly from Latin porphyrites
Class
Metamorphic Rocks
Igneous Rocks
Sub-Class
Durable Rock, Medium Hardness Rock
Durable Rock, Hard Rock
Family
Group
Not Applicable
Plutonic
Other Categories
Coarse Grained Rock, Fine Grained Rock, Medium Grained Rock, Opaque Rock
Fine Grained Rock, Opaque Rock
Texture
Texture
Foliated, Platy
Porphyritic
Color
Black, Blue, Brown, Dark Brown, Green, Grey, Silver
Black, Brown, Colourless, Green, Grey, Red, Rust, White
Maintenance
Less
Less
Durability
Durable
Durable
Water Resistant
Yes
No
Scratch Resistant
No
Yes
Stain Resistant
No
Yes
Wind Resistant
No
No
Acid Resistant
No
Yes
Appearance
Layered and Shiny
Dull
Uses
Architecture
Interior Uses
Decorative Aggregates, Floor Tiles, Interior Decoration
Decorative Aggregates, Interior Decoration
Exterior Uses
Garden Decoration, Paving Stone
Garden Decoration, Paving Stone
Other Architectural Uses
Not Yet Used
Curbing
Industry
Construction Industry
As Dimension Stone, Building houses or walls, Cement Manufacture, for Road Aggregate, Roadstone
Construction Aggregate
Medical Industry
Not Yet Used
Not Yet Used
Antiquity Uses
Artifacts
Artifacts, Monuments, Sculpture
Other Uses
Commercial Uses
Used in aquariums, Writing Slates
Creating Artwork, Gemstone, Jewelry
Types
Types
Mica Schists, Calc-Silicate Schists, Graphite Schists, Blueschists, Whiteschists, Greenschists, Hornblende Schist, Talc Schist, Chlorite Schist, Garnet Schist, Glaucophane schist.
Rhomb Porphyry
Features
Easily splits into thin plates, Smooth to touch
Generally rough to touch, Is one of the oldest rock, Surfaces are often shiny
Archaeological Significance
Monuments
Not Yet Used
Used
Famous Monuments
Not Applicable
Data Not Available
Sculpture
Not Yet Used
Used
Famous Sculptures
Not Applicable
Data Not Available
Pictographs
Used
Not Used
Petroglyphs
Used
Not Used
Figurines
Not Yet Used
Used
Fossils
Absent
Absent
Formation
Formation
Schist formed by dynamic metamorphism at high temperatures and pressures that aligns the grains of mica, hornblende and other elongated minerals into thin layers.
Porphyry is formed in two stages: the magma cools slowly deep within the crust or the magma is cools rapidly as it erupts from a volcano, creating small grains that are usually invisible to naked eye.
Composition
Mineral Content
Alusite, Amphibole, Biotite, Chlorite, Epidote, Feldspar, Garnet, Graphite, Hornblade, Kyanite, Micas, Muscovite or Illite, Porphyroblasts, Quartz, Sillimanite, Staurolite, Talc
Biotite, Chert, Feldspar, Garnet, Graphite, Quartz, Silica
Compound Content
CaO, Carbon Dioxide, MgO
Aluminium Oxide, CaO, Iron(III) Oxide, Potassium Oxide, MgO, Sodium Oxide, Silicon Dioxide, Titanium Dioxide
Transformation
Metamorphism
No
Yes
Types of Metamorphism
Not Applicable
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism, Hydrothermal Metamorphism, Impact Metamorphism, Regional Metamorphism
Weathering
Yes
Yes
Types of Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Biological Weathering, Chemical Weathering, Not Registered
Erosion
Yes
Yes
Types of Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion
Properties
Physical Properties
Hardness
3.5-4
6-7
Grain Size
Medium to Fine Coarse Grained
Fine Grained
Fracture
Conchoidal
Irregular
Streak
White
White
Porosity
Highly Porous
Less Porous
Luster
Shiny
Dull
Cleavage
Slaty
Imperfect
Toughness
1.5
1.7
Specific Gravity
2.5-2.9
2.5-4
Transparency
Opaque
Translucent to Opaque
Density
2.8-2.9 g/cm3
2.5-2.52 g/cm3
Thermal Properties
Resistance
Impact Resistant, Pressure Resistant, Water Resistant
Heat Resistant, Impact Resistant
Reserves
Deposits in Eastern Continents
Asia
Afghanistan, Bangladesh, Bhutan, China, India, Japan, Kazakhstan, Malaysia, Pakistan, Russia, Thailand, Turkey, Vietnam
China, Kazakhstan, South Korea, Thailand, Turkey, Vietnam
Africa
Egypt, Ethiopia, Morocco, Nigeria, South Africa
Egypt, Ethiopia, Ghana, South Africa
Europe
Austria, England, France, Georgia, Germany, Italy, Liechtenstein, Monaco, Norway, Slovenia, Spain, Sweden, Switzerland
Finland, France, Germany, Great Britain, Hungary, Iceland, Ireland, Italy, Netherlands, Norway, Romania, Sweden, Switzerland
Others
Not Yet Found
Greenland
Deposits in Western Continents
North America
Canada, Costa Rica, Cuba, Mexico, Panama, USA
Canada, Cuba, Jamaica, USA
South America
Brazil, Colombia, Guyana
Bolivia, Brazil, Colombia, Ecuador, Paraguay
Deposits in Oceania Continent
Australia
New South Wales, New Zealand, Queensland
New South Wales, New Zealand, Western Australia
All about Schist and Porphyry Properties
Know all about Schist and Porphyry properties here. All properties of rocks are important as they define the type of rock and its application. Schist belongs to Metamorphic Rocks while Porphyry belongs to Igneous Rocks.Texture of Schist is Foliated, Platy whereas that of Porphyry is Porphyritic. Schist appears Layered and Shiny and Porphyry appears Dull. The luster of Schist is shiny while that of Porphyry is dull. Schist is available in black, blue, brown, dark brown, green, grey, silver colors whereas Porphyry is available in black, brown, colourless, green, grey, red, rust, white colors. The commercial uses of Schist are used in aquariums, writing slates and that of Porphyry are creating artwork, gemstone, jewelry.
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