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Porphyry and Hornfels


Hornfels and Porphyry


Definition

Definition
Porphyry is a reddish-brown to purple igneous rock containing large phenocrysts of various minerals embedded in a fine-grained matrix   
Hornfels is a metamorphic rock formed by the contact between mudstone or other clay rich rock, and a hot igneous body, and represents a heat altered equivalent of the original rock   

History
  
  

Origin
Egypt   
New Zealand   

Discoverer
Unknown   
Unknown   

Etymology
From Old French porfire, from Italian porfiro and in some cases directly from Latin porphyrites   
From German which means hornstone   

Class
Igneous Rocks   
Metamorphic Rocks   

Sub-Class
Durable Rock, Hard Rock   
Durable Rock, Soft Rock   

Family
  
  

Group
Plutonic   
Not Applicable   

Other Categories
Fine Grained Rock, Opaque Rock   
Fine Grained Rock, Opaque Rock   

Texture

Texture
Porphyritic   
Granular, Platy   

Color
Black, Brown, Colourless, Green, Grey, Red, Rust, White   
Brown, Dark Greenish - Grey, Green, Reddish Brown   

Maintenance
Less   
Less   

Durability
Durable   
Durable   

Water Resistant
No   
Yes   

Scratch Resistant
Yes   
No   

Stain Resistant
Yes   
No   

Wind Resistant
No   
No   

Acid Resistant
Yes   
No   

Appearance
Dull   
Dull   

Uses

Architecture
  
  

Interior Uses
Decorative Aggregates, Interior Decoration   
Decorative Aggregates, Flooring, Homes, Interior Decoration   

Exterior Uses
Garden Decoration, Paving Stone   
As Building Stone, As Facing Stone, Garden Decoration, Office Buildings, Paving Stone   

Other Architectural Uses
Curbing   
Curbing   

Industry
  
  

Construction Industry
Construction Aggregate   
for Road Aggregate, Roadstone   

Medical Industry
Not Yet Used   
Not Yet Used   

Antiquity Uses
Artifacts, Monuments, Sculpture   
Artifacts, Monuments   

Other Uses
  
  

Commercial Uses
Creating Artwork, Gemstone, Jewelry   
Cemetery Markers, Commemorative Tablets, Creating Artwork   

Types

Types
Rhomb Porphyry   
Biotite hornfels   

Features
Generally rough to touch, Is one of the oldest rock, Surfaces are often shiny   
Smooth to touch   

Archaeological Significance
  
  

Monuments
Used   
Used   

Famous Monuments
Data Not Available   
Data Not Available   

Sculpture
Used   
Not Yet Used   

Famous Sculptures
Data Not Available   
Not Applicable   

Pictographs
Not Used   
Used   

Petroglyphs
Not Used   
Used   

Figurines
Used   
Not Yet Used   

Fossils
Absent   
Absent   

Formation

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.   
Due to change in environmental conditions, rocks are heated and pressurized deep inside the Earth's surface. Hornfels is formed from the extreme heat caused by magma or by the intense collisions and friction of tectonic plates.   

Composition
  
  

Mineral Content
Biotite, Chert, Feldspar, Garnet, Graphite, Quartz, Silica   
Andalusite   

Compound Content
Aluminium Oxide, CaO, Iron(III) Oxide, Potassium Oxide, MgO, Sodium Oxide, Silicon Dioxide, Titanium Dioxide   
Fe, Mg   

Transformation
  
  

Metamorphism
Yes   
No   

Types of Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism, Hydrothermal Metamorphism, Impact Metamorphism, Regional Metamorphism   
Not Applicable   

Weathering
Yes   
Yes   

Types of Weathering
Biological Weathering, Chemical Weathering, Not Registered   
Biological Weathering   

Erosion
Yes   
Yes   

Types of Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion   
Chemical Erosion, Glacier Erosion, Sea Erosion, Water Erosion, Wind Erosion   

Properties

Physical Properties
  
  

Hardness
6-7   
2-3   

Grain Size
Fine Grained   
Fine Grained   

Fracture
Irregular   
Conchoidal   

Streak
White   
Unknown   

Porosity
Less Porous   
Highly Porous   

Luster
Dull   
Shiny   

Compressive Strength
Not Available   
5.80 N/mm2   
31

Cleavage
Imperfect   
Perfect   

Toughness
1.7   
Not Yet Found   

Specific Gravity
2.5-4   
3.4-3.9   

Transparency
Translucent to Opaque   
Opaque   

Density
2.5-2.52 g/cm3   
0.25-0.30 g/cm3   

Thermal Properties
  
  

Specific Heat Capacity
Not Available   
0.84 kJ/Kg K   
15

Resistance
Heat Resistant, Impact Resistant   
Heat Resistant, Impact Resistant, Pressure Resistant   

Reserves

Deposits in Eastern Continents
  
  

Asia
China, Kazakhstan, South Korea, Thailand, Turkey, Vietnam   
Bangladesh, Bhutan, China, India, North Korea, Qatar, Russia, Saudi Arabia, South Korea, Thailand   

Africa
Egypt, Ethiopia, Ghana, South Africa   
Cameroon, East Africa, Tanzania, Western Africa   

Europe
Finland, France, Germany, Great Britain, Hungary, Iceland, Ireland, Italy, Netherlands, Norway, Romania, Sweden, Switzerland   
United Kingdom   

Others
Greenland   
Not Yet Found   

Deposits in Western Continents
  
  

North America
Canada, Cuba, Jamaica, USA   
Canada, USA   

South America
Bolivia, Brazil, Colombia, Ecuador, Paraguay   
Bolivia, Brazil, Colombia, Ecuador   

Deposits in Oceania Continent
  
  

Australia
New South Wales, New Zealand, Western Australia   
New South Wales, New Zealand, Queensland, Western Australia   

Summary >>
<< Reserves

All about Porphyry and Hornfels Properties

Know all about Porphyry and Hornfels properties here. All properties of rocks are important as they define the type of rock and its application. Porphyry belongs to Igneous Rocks while Hornfels belongs to Metamorphic Rocks.Texture of Porphyry is Porphyritic whereas that of Hornfels is Granular, Platy. Porphyry appears Dull and Hornfels appears Dull. The luster of Porphyry is dull while that of Hornfels is shiny. Porphyry is available in black, brown, colourless, green, grey, red, rust, white colors whereas Hornfels is available in brown, dark greenish - grey, green, reddish brown colors. The commercial uses of Porphyry are creating artwork, gemstone, jewelry and that of Hornfels are cemetery markers, commemorative tablets, creating artwork.

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