Definition
Skarns are formed during regional or contact metamorphism and from a variety of metasomatic processes involving fluids of magmatic, metamorphic, and/or marine origin
Porphyry is a reddish-brown to purple igneous rock containing large phenocrysts of various minerals embedded in a fine-grained matrix
History
Origin
USA, Australia
Egypt
Discoverer
Tornebohm
Unknown
Etymology
From an old Swedish mining term originally used to describe a type of silicate gangue or waste rock.
From Old French porfire, from Italian porfiro and in some cases directly from Latin porphyrites
Class
Metamorphic Rocks
Igneous Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Hard Rock
Family
Group
-
Plutonic
Other Categories
Fine Grained Rock, Opaque Rock
Fine Grained Rock, Opaque Rock
Texture
Earthy, Mud-rich, Rough
Porphyritic
Color
Black, Brown, Green, Grey, White
Black, Brown, Green, Grey, Red, Rust, White
Maintenance
Less
Less
Durability
Durable
Durable
Water Resistant
✔
✘
✔
✘
Scratch Resistant
✔
✘
✔
✘
Stain Resistant
✔
✘
✔
✘
Wind Resistant
✔
✘
✔
✘
Acid Resistant
✔
✘
✔
✘
Appearance
Dull
Dull
Architecture
Interior Uses
Decorative Aggregates, Entryways, Interior Decoration
Decorative Aggregates, Interior Decoration
Exterior Uses
As Building Stone, As Facing Stone, Garden Decoration, Paving Stone
Garden Decoration, Paving Stone
Other Architectural Uses
Curbing
Curbing
Industry
Construction Industry
As a Flux in the Production of Steel and Pig Iron, As a Sintering Agent in Steel Industry to process Iron Ore, As Dimension Stone, Gold and Silver production, Manufacture of Magnesium and Dolomite Refractories
Construction Aggregate
Medical Industry
-
-
Antiquity Uses
Artifacts, Monuments, Sculpture
Artifacts, Monuments, Sculpture
Other Uses
Commercial Uses
Creating Artwork, Gemstone, Jewelry, Metallurgical Flux, Source of Magnesia (MgO)
Creating Artwork, Gemstone, Jewelry
Types
Endoskarns
Rhomb Porphyry
Features
Host Rock for Lead, Zinc and Copper Deposits
Generally rough to touch, Is one of the oldest rock, Surfaces are often shiny
Archaeological Significance
Monuments
-
-
Famous Monuments
-
-
Sculpture
-
-
Famous Sculptures
-
-
Pictographs
-
-
Petroglyphs
-
-
Figurines
-
-
Fossils
Absent
Absent
Formation
Due to change in environmental conditions, rocks are heated and pressurized deep inside the Earth's surface. Skarn is formed from the extreme heat caused by magma or by the intense collisions and friction of tectonic plates.
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.
Composition
Mineral Content
Calcite, Enstatite, Epidote, Garnet, Magnetite, Pyroxene, Titanite
Biotite, Chert, Feldspar, Garnet, Graphite, Quartz, Silica
Compound Content
Au, CaO, Carbon Dioxide, Cu, Fe, MgO
Aluminium Oxide, CaO, Iron(III) Oxide, Potassium Oxide, MgO, Sodium Oxide, Silicon Dioxide, Titanium Dioxide
Transformation
Metamorphism
✔
✘
✔
✘
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
✔
✘
✔
✘
Types of Weathering
-
Biological Weathering, Chemical Weathering
Erosion
✔
✘
✔
✘
Types of Erosion
-
Chemical Erosion, Coastal Erosion, Glacier Erosion
Physical Properties
Hardness
6.56-7
1
7
👆🏻
Grain Size
Fine Grained
Fine Grained
Fracture
Irregular
Irregular
Streak
Light to dark brown
White
Porosity
Less Porous
Less Porous
Luster
Waxy and Dull
Dull
Compressive Strength
70.00 N/mm2150.00 N/mm2
0.15
450
👆🏻
Cleavage
Slaty
-
Toughness
2.4
1.7
Specific Gravity
2.862.5-4
0
8.4
👆🏻
Transparency
Opaque
Translucent to Opaque
Density
2.8-2.9 g/cm32.5-2.52 g/cm3
0
1400
👆🏻
Thermal Properties
Specific Heat Capacity
0.92 kJ/Kg K0.71 kJ/Kg K
0.14
3.2
👆🏻
Resistance
Heat Resistant
Heat Resistant, Impact Resistant
Deposits in Eastern Continents
Asia
China, India, Russia, Saudi Arabia, South Korea, Sri Lanka
China, Kazakhstan, South Korea, Thailand, Turkey, Vietnam
Africa
South Africa, Western Africa
Egypt, Ethiopia, Ghana, South Africa
Europe
United Kingdom
Finland, France, Germany, Great Britain, Hungary, Iceland, Ireland, Italy, Netherlands, Norway, Romania, Sweden, Switzerland
Others
-
Greenland
Deposits in Western Continents
North America
Canada
Canada, Cuba, Jamaica, USA
South America
Brazil, Colombia, Paraguay
Bolivia, Brazil, Colombia, Ecuador, Paraguay
Deposits in Oceania Continent
Australia
Central Australia, Western Australia
New South Wales, New Zealand, Western Australia