Porphyry and Rhyodacite
Definition
Definition
Porphyry is a reddish-brown to purple igneous rock containing large phenocrysts of various minerals embedded in a fine-grained matrix
Rhyodacite is an extrusive volcanic rock intermediate in composition between dacite and rhyolite
History
Origin
Egypt
USA
Discoverer
Unknown
Unknown
Etymology
From Old French porfire, from Italian porfiro and in some cases directly from Latin porphyrites
Rhyo lite + dacite : a rock intermediate between rhyolite and dacite that is the extrusive equivalent of granodiorite
Class
Igneous Rocks
Igneous Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Medium Hardness Rock
Family
Group
Plutonic
Volcanic
Other Categories
Fine Grained Rock, Opaque Rock
Fine Grained Rock, Opaque Rock
Texture
Texture
Porphyritic
Earthy
Color
Black, Brown, Colourless, Green, Grey, Red, Rust, White
Black to Grey, Dark Greenish - Grey
Maintenance
Less
More
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
Skeletal
Uses
Architecture
Interior Uses
Decorative Aggregates, Interior Decoration
Decorative Aggregates, Interior Decoration
Exterior Uses
Garden Decoration, Paving Stone
As Building Stone, Garden Decoration
Other Architectural Uses
Curbing
Curbing
Industry
Construction Industry
Construction Aggregate
As Dimension Stone, Construction Aggregate, for Road Aggregate, Landscaping
Medical Industry
Not Yet Used
Not Yet Used
Antiquity Uses
Artifacts, Monuments, Sculpture
Artifacts
Other Uses
Commercial Uses
Creating Artwork, Gemstone, Jewelry
Cemetery Markers, Creating Artwork
Types
Types
Rhomb Porphyry
Not Available
Features
Generally rough to touch, Is one of the oldest rock, Surfaces are often shiny
Available in Lots of Colors and Patterns
Archaeological Significance
Monuments
Used
Not Yet Used
Famous Monuments
Data Not Available
Not Applicable
Sculpture
Used
Not Yet Used
Famous Sculptures
Data Not Available
Not Applicable
Pictographs
Not Used
Used
Petroglyphs
Not Used
Used
Figurines
Used
Not Yet 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.
Rhyodacite is a fine-grained, hard rock which is a type of metasomatite, essentially altered basalt. It forms with or without crystallization, either below the surface as intrusive rocks or on the surface as extrusive rocks.
Composition
Mineral Content
Biotite, Chert, Feldspar, Garnet, Graphite, Quartz, Silica
Amphibole, Apatite, Biotite, Feldspar, Garnet, Hornblade, Magnetite, Plagioclase, Pyroxene, Quartz, Zircon
Compound Content
Aluminium Oxide, CaO, Iron(III) Oxide, Potassium Oxide, MgO, Sodium Oxide, Silicon Dioxide, Titanium Dioxide
Ca, Fe, Potassium Oxide, NA, Potassium, Silicon Dioxide
Transformation
Metamorphism
Yes
Yes
Types of Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism, Hydrothermal Metamorphism, Impact Metamorphism, Regional Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism, Hydrothermal Metamorphism, Impact Metamorphism, Regional Metamorphism
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, Coastal Erosion, Glacier Erosion
Properties
Physical Properties
Hardness
6-7
5.5-6
Grain Size
Fine Grained
Fine Grained
Fracture
Irregular
Conchoidal
Streak
White
Black
Porosity
Less Porous
Less Porous
Luster
Dull
Greasy to Dull
Compressive Strength
Not Available
200.50 N/mm2
9
Cleavage
Imperfect
Not Available
Toughness
1.7
2.1
Specific Gravity
2.5-4
2.34-2.40
Transparency
Translucent to Opaque
Opaque
Density
2.5-2.52 g/cm3
Not Available
Thermal Properties
Specific Heat Capacity
Not Available
1.12 kJ/Kg K
7
Resistance
Heat Resistant, Impact Resistant
Heat Resistant
Reserves
Deposits in Eastern Continents
Asia
China, Kazakhstan, South Korea, Thailand, Turkey, Vietnam
China, India, Iran, Saudi Arabia, Sri Lanka, Taiwan, Thailand, Turkey, Vietnam
Africa
Egypt, Ethiopia, Ghana, South Africa
Angola, Egypt, Madagascar, Namibia, Nigeria, South Africa
Europe
Finland, France, Germany, Great Britain, Hungary, Iceland, Ireland, Italy, Netherlands, Norway, Romania, Sweden, Switzerland
Austria, Belgium, Finland, France, Germany, Italy, Norway, Sardinia, Spain, Switzerland
Others
Greenland
Not Yet Found
Deposits in Western Continents
North America
Canada, Cuba, Jamaica, USA
Canada, USA
South America
Bolivia, Brazil, Colombia, Ecuador, Paraguay
Not Yet Found
Deposits in Oceania Continent
Australia
New South Wales, New Zealand, Western Australia
Not Yet Found
All about Porphyry and Rhyodacite Properties
Know all about Porphyry and Rhyodacite properties here. All properties of rocks are important as they define the type of rock and its application. Porphyry and Rhyodacite belong to Igneous Rocks.Texture of Porphyry is Porphyritic whereas that of Rhyodacite is Earthy. Porphyry appears Dull and Rhyodacite appears Skeletal. The luster of Porphyry is dull while that of Rhyodacite is greasy to dull. Porphyry is available in black, brown, colourless, green, grey, red, rust, white colors whereas Rhyodacite is available in black to grey, dark greenish - grey colors. The commercial uses of Porphyry are creating artwork, gemstone, jewelry and that of Rhyodacite are cemetery markers, creating artwork.
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