Definition
Porphyry is a reddish-brown to purple igneous rock containing large phenocrysts of various minerals embedded in a fine-grained matrix
Very fine grained fault rock which is composed of glassy matrix that often contains inclusions of wall-rock fragments.
Discoverer
Unknown
Unknown
Etymology
From Old French porfire, from Italian porfiro and in some cases directly from Latin porphyrites
From pseudo- + tachylite, a glassy rock generated by frictional heat within faults.
Class
Igneous Rocks
Metamorphic Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Hard Rock
Other Categories
Fine Grained Rock, Opaque Rock
Fine Grained Rock, Opaque Rock
Texture
Porphyritic
Quench
Color
Black, Brown, Green, Grey, Red, Rust, White
Black, Brown, Green, Grey, Pink, White
Durability
Durable
Durable
Scratch Resistant
Yes
Yes
Appearance
Dull
Dull and Soft
Interior Uses
Decorative Aggregates, Interior Decoration
Decorative Aggregates, Entryways, Interior Decoration
Exterior Uses
Garden Decoration, Paving Stone
As Building Stone, As Facing Stone, Garden Decoration
Other Architectural Uses
Curbing
Curbing
Construction Industry
Construction Aggregate
As Dimension Stone, Cement Manufacture, for Road Aggregate, Making natural cement
Antiquity Uses
Artifacts, Monuments, Sculpture
Artifacts, Monuments
Commercial Uses
Creating Artwork, Gemstone, Jewelry
Creating Artwork, Gemstone
Types
Rhomb Porphyry
Cataclastic rock
Features
Generally rough to touch, Is one of the oldest rock, Surfaces are often shiny
Host Rock for Lead
Archaeological Significance
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.
Due to change in environmental conditions, rocks are heated and pressurized deep inside the Earth's surface. Pseudotachylite is formed from the extreme heat caused by magma or by the intense collisions and friction of tectonic plates.
Mineral Content
Biotite, Chert, Feldspar, Garnet, Graphite, Quartz, Silica
Iron Oxides, Pyroxene, Quartz, Stishovite, Sulfides
Compound Content
Aluminium Oxide, CaO, Iron(III) Oxide, Potassium Oxide, MgO, Sodium Oxide, Silicon Dioxide, Titanium Dioxide
Carbon Dioxide, Silicon Dioxide, Sulfur Dioxide, Sulphur
Types of Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism, Hydrothermal Metamorphism, Impact Metamorphism, Regional Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism
Types of Weathering
Biological Weathering, Chemical Weathering
-
Types of Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion
-
Grain Size
Fine Grained
Very fine-grained
Fracture
Irregular
Uneven
Streak
White
Light to dark brown
Porosity
Less Porous
Less Porous
Specific Gravity
2.5-4
2.46-2.86
Transparency
Translucent to Opaque
Transparent to Translucent
Density
2.5-2.52 g/cm3
2.7-2.9 g/cm3
Resistance
Heat Resistant, Impact Resistant
Heat Resistant
Deposits in Eastern Continents
Asia
China, Kazakhstan, South Korea, Thailand, Turkey, Vietnam
South Korea
Africa
Egypt, Ethiopia, Ghana, South Africa
Western Africa
Europe
Finland, France, Germany, Great Britain, Hungary, Iceland, Ireland, Italy, Netherlands, Norway, Romania, Sweden, Switzerland
Great Britain, Switzerland
Deposits in Western Continents
North America
Canada, Cuba, Jamaica, USA
-
South America
Bolivia, Brazil, Colombia, Ecuador, Paraguay
-
Deposits in Oceania Continent
Australia
New South Wales, New Zealand, Western Australia
Central Australia, Western Australia
All about Porphyry and Pseudotachylite Properties
Know all about Porphyry and Pseudotachylite properties here. All properties of rocks are important as they define the type of rock and its application. Porphyry belongs to Igneous Rocks while Pseudotachylite belongs to Metamorphic Rocks.Texture of Porphyry is Porphyritic whereas that of Pseudotachylite is Quench. Porphyry appears Dull and Pseudotachylite appears Dull and Soft. The luster of Porphyry is dull while that of Pseudotachylite is vitreous. Porphyry is available in black, brown, green, grey, red, rust, white colors whereas Pseudotachylite is available in black, brown, green, grey, pink, white colors. The commercial uses of Porphyry and Pseudotachylite are creating artwork, gemstone, jewelry.