Definition
Porphyry is a reddish-brown to purple igneous rock containing large phenocrysts of various minerals embedded in a fine-grained matrix
Gossan is intensely oxidized, weathered or decomposed rock, usually the upper and exposed part of an ore deposit or mineral vein.
Discoverer
Unknown
Cornish Gossen
Etymology
From Old French porfire, from Italian porfiro and in some cases directly from Latin porphyrites
From Cornish gossen from gos, blood from Old Cornish guit
Class
Igneous Rocks
Metamorphic Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Medium Hardness Rock
Other Categories
Fine Grained Rock, Opaque Rock
Fine Grained Rock, Medium Grained Rock, Opaque Rock
Texture
Porphyritic
Rough, Sandy
Color
Black, Brown, Green, Grey, Red, Rust, White
Brown, Brown- Black, Gold, Green, Rust
Durability
Durable
Durable
Scratch Resistant
Yes
Yes
Appearance
Dull
Dull and Banded
Interior Uses
Decorative Aggregates, Interior Decoration
Countertops, Decorative Aggregates, Interior Decoration
Exterior Uses
Garden Decoration, Paving Stone
As Building Stone, As Facing Stone, Paving Stone, Garden Decoration, Office Buildings
Other Architectural Uses
Curbing
Curbing
Construction Industry
Construction Aggregate
As Dimension Stone, Cement Manufacture, Construction Aggregate, for Road Aggregate
Antiquity Uses
Artifacts, Monuments, Sculpture
Artifacts
Commercial Uses
Creating Artwork, Gemstone, Jewelry
Cemetery Markers, Commemorative Tablets, Gemstone
Types
Rhomb Porphyry
Translocated gossan and Leakage gossan
Features
Generally rough to touch, Is one of the oldest rock, Surfaces are often shiny
Clasts are smooth to touch, Easily splits into thin plates
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.
Earth movements can cause rocks to be either deeply buried or squeezed and hence the rocks are heated and put under great pressure.
Mineral Content
Biotite, Chert, Feldspar, Garnet, Graphite, Quartz, Silica
Apatite, Augite, Biotite, Bronzite, Calcite, Chert, Epidote, Feldspar, Hornblende, Micas, Plagioclase, Pyroxene, Quartz, Sulfides, Zircon
Compound Content
Aluminium Oxide, CaO, Iron(III) Oxide, Potassium Oxide, MgO, Sodium Oxide, Silicon Dioxide, Titanium Dioxide
Aluminium Oxide, CaO, Fe, FeO, Silicon Dioxide, Sulphur
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
-
Types of Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion
Chemical Erosion, Sea Erosion, Wind Erosion
Grain Size
Fine Grained
Fine to Medium Grained
Fracture
Irregular
Conchoidal
Streak
White
White to Grey
Porosity
Less Porous
Highly Porous
Specific Gravity
2.5-4
2.0
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, Indonesia, Russia, Singapore, South Korea
Africa
Egypt, Ethiopia, Ghana, South Africa
Cape Verde, Ethiopia, Ghana, South Africa, Western Africa
Europe
Finland, France, Germany, Great Britain, Hungary, Iceland, Ireland, Italy, Netherlands, Norway, Romania, Sweden, Switzerland
Albania, France, Germany, Great Britain, United Kingdom
Deposits in Western Continents
North America
Canada, Cuba, Jamaica, USA
Canada, USA
South America
Bolivia, Brazil, Colombia, Ecuador, Paraguay
Brazil, Colombia, Ecuador
Deposits in Oceania Continent
Australia
New South Wales, New Zealand, Western Australia
New South Wales, South Australia, Western Australia
Porphyry vs Gossan Characteristics
Though some rocks look identical, they have certain characteristics which distinguish them from others. Characteristics of rocks include texture, appearance, color, fracture, streak, hardness etc. Porphyry vs Gossan characteristics assist us to distinguish and recognize rocks. Also you can check about Properties of Porphyry and Properties of Gossan. Learn more about Porphyry vs Gossan in the next section. The interior uses of Porphyry include Decorative aggregates and Interior decoration whereas the interior uses of Gossan include Countertops, Decorative aggregates and Interior decoration. Due to some exceptional properties of Porphyry and Gossan, they have various applications in construction industry. The uses of Porphyry in construction industry include Construction aggregate and that of Gossan include As dimension stone, Cement manufacture, Construction aggregate, For road aggregate.
More about Porphyry and Gossan
Here you can know more about Porphyry and Gossan. The life cycle of a rock consists of formation of rock, composition of rock and transformation of rock. The composition of Porphyry and Gossan consists of mineral content and compound content. The mineral content of Porphyry includes Biotite, Chert, Feldspar, Garnet, Graphite, Quartz, Silica and mineral content of Gossan includes Apatite, Augite, Biotite, Bronzite, Calcite, Chert, Epidote, Feldspar, Hornblende, Micas, Plagioclase, Pyroxene, Quartz, Sulfides, Zircon. You can also check out the list of all Igneous Rocks. When we have to compare Porphyry vs Gossan, the texture, color and appearance plays an important role in determining the type of rock. Porphyry is available in black, brown, green, grey, red, rust, white colors whereas, Gossan is available in brown, brown- black, gold, green, rust colors. Appearance of Porphyry is Dull and that of Gossan is Dull and Banded. Properties of rock is another aspect for Porphyry vs Gossan. The hardness of Porphyry is 6-7 and that of Gossan is 4-5. The types of Porphyry are Rhomb Porphyry whereas types of Gossan are Translocated gossan and Leakage gossan. Streak of rock is the color of powder produced when it is dragged across an unweathered surface. The streak of Porphyry is white while that of Gossan is white to grey. The specific heat capacity of Porphyry is 0.71 kJ/Kg K and that of Gossan is 0.24 kJ/Kg K. Depending on the properties like hardness, toughness, specific heat capacity, porosity etc., rocks are resistant to heat, wear, impact, etc.Porphyry is heat resistant, impact resistant whereas Gossan is heat resistant, impact resistant, pressure resistant.