Definition
Very fine grained fault rock which is composed of glassy matrix that often contains inclusions of wall-rock fragments.
Porphyry is a reddish-brown to purple igneous rock containing large phenocrysts of various minerals embedded in a fine-grained matrix
Discoverer
Unknown
Unknown
Etymology
From pseudo- + tachylite, a glassy rock generated by frictional heat within faults.
From Old French porfire, from Italian porfiro and in some cases directly from Latin porphyrites
Class
Metamorphic Rocks
Igneous Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Hard Rock
Group
Not Applicable
Plutonic
Other Categories
Fine Grained Rock, Opaque Rock
Fine Grained Rock, Opaque Rock
Texture
Quench
Porphyritic
Color
Black, Brown, Colourless, Green, Grey, Pink, White
Black, Brown, Colourless, Green, Grey, Red, Rust, White
Durability
Durable
Durable
Scratch Resistant
Yes
Yes
Appearance
Dull and Soft
Dull
Interior Uses
Decorative Aggregates, Entryways, Interior Decoration
Decorative Aggregates, Interior Decoration
Exterior Uses
As Building Stone, As Facing Stone, Garden Decoration
Garden Decoration, Paving Stone
Other Architectural Uses
Curbing
Curbing
Construction Industry
As Dimension Stone, Cement Manufacture, for Road Aggregate, Making natural cement
Construction Aggregate
Medical Industry
Not Yet Used
Not Yet Used
Antiquity Uses
Artifacts, Monuments
Artifacts, Monuments, Sculpture
Commercial Uses
Creating Artwork, Gemstone
Creating Artwork, Gemstone, Jewelry
Types
Not Available
Rhomb Porphyry
Features
Host Rock for Lead
Generally rough to touch, Is one of the oldest rock, Surfaces are often shiny
Archaeological Significance
Famous Monuments
Data Not Available
Data Not Available
Sculpture
Not Yet Used
Used
Famous Sculptures
Not Applicable
Data Not Available
Pictographs
Not Used
Not Used
Petroglyphs
Not Used
Not Used
Figurines
Not Yet Used
Used
Formation
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.
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.
Mineral Content
Iron Oxides, Pyroxene, Quartz, Stishovite, Sulfides
Biotite, Chert, Feldspar, Garnet, Graphite, Quartz, Silica
Compound Content
Carbon Dioxide, Silicon Dioxide, Sulfur Dioxide, Sulphur
Aluminium Oxide, CaO, Iron(III) Oxide, Potassium Oxide, MgO, Sodium Oxide, Silicon Dioxide, Titanium Dioxide
Types of Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism, Hydrothermal Metamorphism, Impact Metamorphism, Regional Metamorphism
Types of Weathering
Not Applicable
Biological Weathering, Chemical Weathering, Not Registered
Types of Erosion
Not Applicable
Chemical Erosion, Coastal Erosion, Glacier Erosion
Grain Size
Very fine-grained
Fine Grained
Fracture
Uneven
Irregular
Streak
Light to dark brown
White
Porosity
Less Porous
Less Porous
Compressive Strength
Not Available
Cleavage
Irregular
Imperfect
Toughness
Not Available
1.7
Specific Gravity
2.46-2.86
2.5-4
Transparency
Transparent to Translucent
Translucent to Opaque
Density
2.7-2.9 g/cm3
2.5-2.52 g/cm3
Specific Heat Capacity
Not Available
Resistance
Heat Resistant
Heat Resistant, Impact Resistant
Deposits in Eastern Continents
Asia
South Korea
China, Kazakhstan, South Korea, Thailand, Turkey, Vietnam
Africa
Western Africa
Egypt, Ethiopia, Ghana, South Africa
Europe
Great Britain, 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
Not Yet Found
Canada, Cuba, Jamaica, USA
South America
Not Yet Found
Bolivia, Brazil, Colombia, Ecuador, Paraguay
Deposits in Oceania Continent
Australia
Central Australia, Western Australia
New South Wales, New Zealand, Western Australia
All about Pseudotachylite and Porphyry Properties
Know all about Pseudotachylite and Porphyry properties here. All properties of rocks are important as they define the type of rock and its application. Pseudotachylite belongs to Metamorphic Rocks while Porphyry belongs to Igneous Rocks.Texture of Pseudotachylite is Quench whereas that of Porphyry is Porphyritic. Pseudotachylite appears Dull and Soft and Porphyry appears Dull. The luster of Pseudotachylite is vitreous while that of Porphyry is dull. Pseudotachylite is available in black, brown, colourless, green, grey, pink, white colors whereas Porphyry is available in black, brown, colourless, green, grey, red, rust, white colors. The commercial uses of Pseudotachylite are creating artwork, gemstone and that of Porphyry are creating artwork, gemstone, jewelry.