Definition
Porphyry is a reddish-brown to purple igneous rock containing large phenocrysts of various minerals embedded in a fine-grained matrix
Gritstone or grit is a hard, coarse-grained, siliceous sandstone
Origin
Egypt
Pennines, England
Discoverer
Unknown
J.J. Ferber
Etymology
From Old French porfire, from Italian porfiro and in some cases directly from Latin porphyrites
From Grit + Stone
Class
Igneous Rocks
Sedimentary 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, Opaque Rock
Texture
Porphyritic
Earthy
Color
Black, Brown, Colourless, Green, Grey, Red, Rust, White
Beige, Black, Brown, Colourless, Cream, Dark Brown, Green, Grey, Light Green, Light to Dark Grey, Pink, Red, White, Yellow
Durability
Durable
Durable
Scratch Resistant
Yes
Yes
Appearance
Dull
Layered and Foliated
Interior Uses
Decorative Aggregates, Interior Decoration
Countertops, Decorative Aggregates, Homes, Interior Decoration
Exterior Uses
Garden Decoration, Paving Stone
As Building Stone, Garden Decoration, Office Buildings, Paving Stone
Other Architectural Uses
Curbing
Curbing
Construction Industry
Construction Aggregate
Construction Aggregate, Roadstone
Medical Industry
Not Yet Used
Not Yet Used
Antiquity Uses
Artifacts, Monuments, Sculpture
Artifacts, Monuments, Sculpture
Commercial Uses
Creating Artwork, Gemstone, Jewelry
An Oil and Gas Reservoir, As a Feed Additive for Livestock, Gemstone, Metallurgical Flux, Production of Lime, Soil Conditioner, Source of Magnesia (MgO), Tombstones
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, Generally rough to touch, Very fine grained rock
Archaeological Significance
Famous Monuments
Data Not Available
Data Not Available
Famous Sculptures
Data Not Available
Data Not Available
Pictographs
Not Used
Not Used
Petroglyphs
Not Used
Not 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.
Gritstone is a type of sedimentary rock which was formed on the floors of wide river deltas where the grit deposits were laid down, with every tide or flood dumping another layer of sediment.
Mineral Content
Biotite, Chert, Feldspar, Garnet, Graphite, Quartz, Silica
Calcite, 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
Not Applicable
Types of Weathering
Biological Weathering, Chemical Weathering, Not Registered
Biological Weathering, Chemical Weathering, Mechanical Weathering
Types of Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion
Chemical Erosion, Coastal Erosion
Grain Size
Fine Grained
Coarse Grained
Fracture
Irregular
Conchoidal
Porosity
Less Porous
Highly Porous
Compressive Strength
Not Available
Cleavage
Imperfect
Perfect
Toughness
1.7
Not Available
Specific Gravity
2.5-4
2.250
Transparency
Translucent to Opaque
Opaque
Density
2.5-2.52 g/cm3
2.2 g/cm3
Specific Heat Capacity
Not Available
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, 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, Western Australia
Porphyry vs Gritstone 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 Gritstone characteristics assist us to distinguish and recognize rocks. Also you can check about Properties of Porphyry and Properties of Gritstone. Learn more about Porphyry vs Gritstone in the next section. The interior uses of Porphyry include Decorative aggregates and Interior decoration whereas the interior uses of Gritstone include Countertops, Decorative aggregates, Homes and Interior decoration. Due to some exceptional properties of Porphyry and Gritstone, they have various applications in construction industry. The uses of Porphyry in construction industry include Construction aggregate and that of Gritstone include Construction aggregate, Roadstone.
More about Porphyry and Gritstone
Here you can know more about Porphyry and Gritstone. The life cycle of a rock consists of formation of rock, composition of rock and transformation of rock. The composition of Porphyry and Gritstone consists of mineral content and compound content. The mineral content of Porphyry includes Biotite, Chert, Feldspar, Garnet, Graphite, Quartz, Silica and mineral content of Gritstone includes Calcite, Clay Minerals, Feldspar, Micas, Quartz. You can also check out the list of all Igneous Rocks. When we have to compare Porphyry vs Gritstone, 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, Gritstone is available in beige, black, brown, colourless, cream, dark brown, green, grey, light green, light to dark grey, pink, red, white, yellow colors. Appearance of Porphyry is Dull and that of Gritstone is Layered and Foliated. Properties of rock is another aspect for Porphyry vs Gritstone. Hardness of Porphyry and Gritstone is 6-7. The types of Porphyry are Rhomb Porphyry whereas types of Gritstone are Not Available. Streak of rock is the color of powder produced when it is dragged across an unweathered surface. The streak of Porphyry and Gritstone is white. The specific heat capacity of Porphyry is Not Available and that of Gritstone is 0.92 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 Gritstone is heat resistant, impact resistant, pressure resistant.