Definition
Porphyry is a reddish-brown to purple igneous rock containing large phenocrysts of various minerals embedded in a fine-grained matrix
Arkose is a sedimentary rock, specifically a type of sandstone containing at least 25% feldspar
Discoverer
Unknown
Alexandre Brongniart
Etymology
From Old French porfire, from Italian porfiro and in some cases directly from Latin porphyrites
From Auvergne region of France used by a French geologist Alexandre Brongniart in 1826 who applied this term to some feldspathic sandstones
Class
Igneous Rocks
Sedimentary Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Hard Rock
Other Categories
Fine Grained Rock, Opaque Rock
Coarse Grained Rock, Opaque Rock
Texture
Porphyritic
Clastic
Color
Black, Brown, Green, Grey, Red, Rust, White
Reddish Brown
Durability
Durable
Durable
Scratch Resistant
Yes
Yes
Appearance
Dull
Rough and Dull
Interior Uses
Decorative Aggregates, Interior Decoration
Decorative Aggregates, Homes, Interior Decoration
Exterior Uses
Garden Decoration, Paving Stone
Paving Stone, Office Buildings
Other Architectural Uses
Curbing
Whetstones
Construction Industry
Construction Aggregate
Cement Manufacture, Construction Aggregate, for Road Aggregate, Production of Glass and Ceramics, Raw material for the manufacture of mortar
Antiquity Uses
Artifacts, Monuments, Sculpture
Artifacts, Sculpture, Small Figurines
Commercial Uses
Creating Artwork, Gemstone, Jewelry
In aquifers, Soil Conditioner, Source of Magnesia (MgO), Tombstones
Types
Rhomb Porphyry
Arkose
Features
Generally rough to touch, Is one of the oldest rock, Surfaces are often shiny
Available in Lots of Colors and Patterns, Generally rough to touch, Is one of the oldest rock
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.
Arkose rock forms from the weathering of feldspar-rich igneous or metamorphic rock, most commonly granitic rocks, which are primarily composed of quartz and feldspar.
Mineral Content
Biotite, Chert, Feldspar, Garnet, Graphite, Quartz, Silica
Calcite, Clay, Clay Minerals, Feldspar, Micas, Quartz
Compound Content
Aluminium Oxide, CaO, Iron(III) Oxide, Potassium Oxide, MgO, Sodium Oxide, Silicon Dioxide, Titanium Dioxide
Aluminium Oxide, CaO, Iron(III) Oxide, Potassium Oxide, MgO, Sodium Oxide, Silicon Dioxide
Types of Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism, Hydrothermal Metamorphism, Impact Metamorphism, Regional Metamorphism
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Types of Weathering
Biological Weathering, Chemical Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Types of Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion
Coastal Erosion, Glacier Erosion, Water Erosion, Wind Erosion
Grain Size
Fine Grained
Coarse Grained
Fracture
Irregular
Conchoidal
Porosity
Less Porous
Highly Porous
Transparency
Translucent to Opaque
Opaque
Density
2.5-2.52 g/cm3
-9999 g/cm3
Resistance
Heat Resistant, Impact Resistant
Heat Resistant, Impact Resistant, Pressure Resistant
Deposits in Eastern Continents
Asia
China, Kazakhstan, South Korea, Thailand, Turkey, Vietnam
China, India, Kazakhstan, Mongolia, Russia, Uzbekistan
Africa
Egypt, Ethiopia, Ghana, South Africa
Namibia, Nigeria, South Africa
Europe
Finland, France, Germany, Great Britain, Hungary, Iceland, Ireland, Italy, Netherlands, Norway, Romania, Sweden, Switzerland
Austria, Denmark, Germany, Great Britain, Netherlands, Norway, Poland, Sweden, Switzerland, United Kingdom
Others
Greenland
Greenland
Deposits in Western Continents
North America
Canada, Cuba, Jamaica, USA
Canada, USA
South America
Bolivia, Brazil, Colombia, Ecuador, Paraguay
Brazil
Deposits in Oceania Continent
Australia
New South Wales, New Zealand, Western Australia
New South Wales, New Zealand