Definition
Porphyry is a reddish-brown to purple igneous rock containing large phenocrysts of various minerals embedded in a fine-grained matrix
Gneiss is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from pre-existing formations that were originally either igneous or sedimentary rocks
Discoverer
Unknown
Unknown
Etymology
From Old French porfire, from Italian porfiro and in some cases directly from Latin porphyrites
From the Middle High German verb gneist (to spark; so called because the rock glitters)
Class
Igneous Rocks
Metamorphic Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Hard Rock
Group
Plutonic
Not Applicable
Other Categories
Fine Grained Rock, Opaque Rock
Coarse Grained Rock, Medium Grained Rock, Opaque Rock
Texture
Porphyritic
Banded, Foliated, Platy
Color
Black, Brown, Colourless, Green, Grey, Red, Rust, White
Black, Brown, Pink, Red, White
Durability
Durable
Durable
Scratch Resistant
Yes
Yes
Interior Uses
Decorative Aggregates, Interior Decoration
Countertops, Decorative Aggregates, Flooring, Interior Decoration
Exterior Uses
Garden Decoration, Paving Stone
As Building Stone, As Facing Stone, Garden Decoration, Paving Stone
Other Architectural Uses
Curbing
Curbing
Construction Industry
Construction Aggregate
As Dimension Stone
Medical Industry
Not Yet Used
Not Yet Used
Antiquity Uses
Artifacts, Monuments, Sculpture
Artifacts
Commercial Uses
Creating Artwork, Gemstone, Jewelry
Cemetery Markers, Jewelry, Tombstones, Used in aquariums
Types
Rhomb Porphyry
Augen Gneiss, Henderson Gneiss, Lewisian Gneiss, Archean and Proterozoic Gneiss.
Features
Generally rough to touch, Is one of the oldest rock, Surfaces are often shiny
Generally rough to touch, Is one of the oldest rock
Archaeological Significance
Famous Monuments
Data Not Available
Konark Sun Temple in India, Washington Monument, US
Sculpture
Used
Not Yet Used
Famous Sculptures
Data Not Available
Not Applicable
Pictographs
Not Used
Not Used
Petroglyphs
Not Used
Not Used
Figurines
Used
Not Yet Used
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.
Gneiss is a high grade metamorphic rock i.e. it has been subjected to higher temperatures and pressures than schist. It is formed by the metamorphosis of Gneiss forms from volcanic rock, shale or granitie.
Mineral Content
Biotite, Chert, Feldspar, Garnet, Graphite, Quartz, Silica
Biotite, Chlorite, Feldspar, Garnet, Graphite, Hornblade, Micas, Muscovite or Illite, Quartz, Quartzite, Silica, Zircon
Compound Content
Aluminium Oxide, CaO, Iron(III) Oxide, Potassium Oxide, MgO, Sodium Oxide, Silicon Dioxide, Titanium Dioxide
Aluminium Oxide, NaCl, CaO, Iron(III) Oxide, FeO, Potassium Oxide, Magnesium Carbonate, MgO, MnO, Phosphorus Pentoxide, Silicon Dioxide, Titanium Dioxide
Types of Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism, Hydrothermal Metamorphism, Impact Metamorphism, Regional Metamorphism
Impact Metamorphism
Types of Weathering
Biological Weathering, Chemical Weathering, Not Registered
Biological Weathering, Mechanical Weathering
Types of Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion
Chemical Erosion, Coastal Erosion, Sea Erosion
Grain Size
Fine Grained
Medium to Coarse Grained
Fracture
Irregular
Irregular
Porosity
Less Porous
Very Less Porous
Compressive Strength
Not Available
Specific Gravity
2.5-4
2.5-2.7
Transparency
Translucent to Opaque
Translucent to Opaque
Density
2.5-2.52 g/cm3
2.6-2.9 g/cm3
Resistance
Heat Resistant, Impact Resistant
Heat Resistant, Pressure Resistant, Scratch Resistant, Wear Resistant
Deposits in Eastern Continents
Asia
China, Kazakhstan, South Korea, Thailand, Turkey, Vietnam
China, India, Iran, Iraq, Kazakhstan, Kyrgyzstan, Mongolia, Russia
Africa
Egypt, Ethiopia, Ghana, South Africa
Cameroon, Ethiopia, Ghana, Kenya, Madagascar, Morocco, Mozambique, Namibia, Nigeria, Tanzania, Togo
Europe
Finland, France, Germany, Great Britain, Hungary, Iceland, Ireland, Italy, Netherlands, Norway, Romania, Sweden, Switzerland
Albania, Austria, Bosnia and Herzegovina, Finland, France, Georgia, Germany, Hungary, Italy, Kosovo, Monaco, Norway, Poland, Romania, Serbia, Slovakia, Slovenia, Switzerland, Ukraine, United Kingdom
Others
Greenland
Not Yet Found
Deposits in Western Continents
North America
Canada, Cuba, Jamaica, USA
Canada, Costa Rica, Cuba, Mexico, Panama, USA
South America
Bolivia, Brazil, Colombia, Ecuador, Paraguay
Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Peru, Venezuela
Deposits in Oceania Continent
Australia
New South Wales, New Zealand, Western Australia
New South Wales, New Zealand, Queensland, Victoria
Porphyry vs Gneiss 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 Gneiss characteristics assist us to distinguish and recognize rocks. Also you can check about Properties of Porphyry and Properties of Gneiss. Learn more about Porphyry vs Gneiss in the next section. The interior uses of Porphyry include Decorative aggregates and Interior decoration whereas the interior uses of Gneiss include Countertops, Decorative aggregates, Flooring and Interior decoration. Due to some exceptional properties of Porphyry and Gneiss, they have various applications in construction industry. The uses of Porphyry in construction industry include Construction aggregate and that of Gneiss include As dimension stone.
More about Porphyry and Gneiss
Here you can know more about Porphyry and Gneiss. The life cycle of a rock consists of formation of rock, composition of rock and transformation of rock. The composition of Porphyry and Gneiss consists of mineral content and compound content. The mineral content of Porphyry includes Biotite, Chert, Feldspar, Garnet, Graphite, Quartz, Silica and mineral content of Gneiss includes Biotite, Chlorite, Feldspar, Garnet, Graphite, Hornblade, Micas, Muscovite or Illite, Quartz, Quartzite, Silica, Zircon. You can also check out the list of all Igneous Rocks. When we have to compare Porphyry vs Gneiss, the texture, color and appearance plays an important role in determining the type of rock. Porphyry is available in black, brown, colourless, green, grey, red, rust, white colors whereas, Gneiss is available in black, brown, pink, red, white colors. Appearance of Porphyry is Dull and that of Gneiss is Foliated. Properties of rock is another aspect for Porphyry vs Gneiss. The hardness of Porphyry is 6-7 and that of Gneiss is 7. The types of Porphyry are Rhomb Porphyry whereas types of Gneiss are Augen Gneiss, Henderson Gneiss, Lewisian Gneiss, Archean and Proterozoic Gneiss.. Streak of rock is the color of powder produced when it is dragged across an unweathered surface. The streak of Porphyry and Gneiss is white. The specific heat capacity of Porphyry is Not Available and that of Gneiss is Not Available. 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 Gneiss is heat resistant, pressure resistant, scratch resistant, wear resistant.