Porphyry and Mylonite
Definition
Definition
Porphyry is a reddish-brown to purple igneous rock containing large phenocrysts of various minerals embedded in a fine-grained matrix
Mylonite is a metamorphic rock formed by ductile deformation during intense shearing encountered during folding and faulting, a process termed cataclastic or dynamic metamorphism
History
Origin
Egypt
New Zealand
Discoverer
Unknown
Unknown
Etymology
From Old French porfire, from Italian porfiro and in some cases directly from Latin porphyrites
From Greek mulōn mill + -ite
Class
Igneous Rocks
Metamorphic Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Medium Hardness Rock
Family
Group
Plutonic
Not Applicable
Other Categories
Fine Grained Rock, Opaque Rock
Fine Grained Rock, Opaque Rock
Texture
Texture
Porphyritic
Foliated
Color
Black, Brown, Colourless, Green, Grey, Red, Rust, White
Black to Grey
Maintenance
Less
Less
Durability
Durable
Durable
Water Resistant
No
Yes
Scratch Resistant
Yes
Yes
Stain Resistant
Yes
No
Wind Resistant
No
No
Acid Resistant
Yes
No
Appearance
Dull
Dull, Banded and Foilated
Uses
Architecture
Interior Uses
Decorative Aggregates, Interior Decoration
Decorative Aggregates, Interior Decoration
Exterior Uses
Garden Decoration, Paving Stone
As Building Stone, As Facing Stone, Paving Stone, Garden Decoration
Other Architectural Uses
Curbing
Curbing
Industry
Construction Industry
Construction Aggregate
for Road Aggregate, Landscaping, Roadstone
Medical Industry
Not Yet Used
Not Yet Used
Antiquity Uses
Artifacts, Monuments, Sculpture
Artifacts, Monuments
Other Uses
Commercial Uses
Creating Artwork, Gemstone, Jewelry
Creating Artwork, Gemstone, Jewelry
Types
Types
Rhomb Porphyry
Blastomylonites, Ultramylonites and Phyllonites
Features
Generally rough to touch, Is one of the oldest rock, Surfaces are often shiny
Surfaces are often shiny
Archaeological Significance
Monuments
Used
Used
Famous Monuments
Data Not Available
Data Not Available
Sculpture
Used
Used
Famous Sculptures
Data Not Available
Data Not Available
Pictographs
Not Used
Used
Petroglyphs
Not Used
Used
Figurines
Used
Used
Fossils
Absent
Absent
Formation
Formation
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.
Mylonites are ductilely deformed rocks formed by the accumulation of large shear strain, in ductile fault zones.
Composition
Mineral Content
Biotite, Chert, Feldspar, Garnet, Graphite, Quartz, Silica
Porphyroblasts
Compound Content
Aluminium Oxide, CaO, Iron(III) Oxide, Potassium Oxide, MgO, Sodium Oxide, Silicon Dioxide, Titanium Dioxide
Aluminium Oxide, Calcium Sulfate, Chromium(III) Oxide, Iron(III) Oxide, Magnesium Carbonate, Silicon Dioxide
Transformation
Metamorphism
Yes
No
Types of Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism, Hydrothermal Metamorphism, Impact Metamorphism, Regional Metamorphism
Not Applicable
Weathering
Yes
Yes
Types of Weathering
Biological Weathering, Chemical Weathering, Not Registered
Biological Weathering, Chemical Weathering, Mechanical Weathering
Erosion
Yes
Yes
Types of Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion
Chemical Erosion, Sea Erosion, Wind Erosion
Properties
Physical Properties
Hardness
6-7
3-4
Grain Size
Fine Grained
Fine Grained
Fracture
Irregular
Conchoidal
Streak
White
White
Porosity
Less Porous
Highly Porous
Luster
Dull
Shiny
Compressive Strength
Not Available
1.28 N/mm2
32
Cleavage
Imperfect
Conchoidal
Toughness
1.7
Not Available
Specific Gravity
2.5-4
2.97-3.05
Transparency
Translucent to Opaque
Opaque
Density
2.5-2.52 g/cm3
2.6-4.8 g/cm3
Thermal Properties
Specific Heat Capacity
Not Available
1.50 kJ/Kg K
3
Resistance
Heat Resistant, Impact Resistant
Heat Resistant, Impact Resistant, Pressure Resistant
Reserves
Deposits in Eastern Continents
Asia
China, Kazakhstan, South Korea, Thailand, Turkey, Vietnam
China, India, Indonesia, Saudi Arabia, South Korea
Africa
Egypt, Ethiopia, Ghana, South Africa
Eritrea, Ethiopia, Ghana, South Africa, Western Africa
Europe
Finland, France, Germany, Great Britain, Hungary, Iceland, Ireland, Italy, Netherlands, Norway, Romania, Sweden, Switzerland
England, Finland, France, Germany, Great Britain, Greece, United Kingdom
Others
Greenland
Not Yet Found
Deposits in Western Continents
North America
Canada, Cuba, Jamaica, USA
USA
South America
Bolivia, Brazil, Colombia, Ecuador, Paraguay
Not Yet Found
Deposits in Oceania Continent
Australia
New South Wales, New Zealand, Western Australia
Central Australia, Western Australia
All about Porphyry and Mylonite Properties
Know all about Porphyry and Mylonite properties here. All properties of rocks are important as they define the type of rock and its application. Porphyry belongs to Igneous Rocks while Mylonite belongs to Metamorphic Rocks.Texture of Porphyry is Porphyritic whereas that of Mylonite is Foliated. Porphyry appears Dull and Mylonite appears Dull, Banded and Foilated. The luster of Porphyry is dull while that of Mylonite is shiny. Porphyry is available in black, brown, colourless, green, grey, red, rust, white colors whereas Mylonite is available in black to grey colors. The commercial uses of Porphyry and Mylonite are creating artwork, gemstone, jewelry.
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