Definition
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
Porphyry is a reddish-brown to purple igneous rock containing large phenocrysts of various minerals embedded in a fine-grained matrix
Discoverer
Unknown
Unknown
Etymology
From German which means hornstone
From Old French porfire, from Italian porfiro and in some cases directly from Latin porphyrites
Class
Metamorphic Rocks
Igneous Rocks
Sub-Class
Durable Rock, Soft Rock
Durable Rock, Hard Rock
Group
Not Applicable
Plutonic
Other Categories
Fine Grained Rock, Opaque Rock
Fine Grained Rock, Opaque Rock
Texture
Granular, Platy
Porphyritic
Color
Brown, Dark Greenish - Grey, Green, Reddish Brown
Black, Brown, Colourless, Green, Grey, Red, Rust, White
Durability
Durable
Durable
Interior Uses
Decorative Aggregates, Flooring, Homes, Interior Decoration
Decorative Aggregates, Interior Decoration
Exterior Uses
As Building Stone, As Facing Stone, Garden Decoration, Office Buildings, Paving Stone
Garden Decoration, Paving Stone
Other Architectural Uses
Curbing
Curbing
Construction Industry
for Road Aggregate, Roadstone
Construction Aggregate
Medical Industry
Not Yet Used
Not Yet Used
Antiquity Uses
Artifacts, Monuments
Artifacts, Monuments, Sculpture
Commercial Uses
Cemetery Markers, Commemorative Tablets, Creating Artwork
Creating Artwork, Gemstone, Jewelry
Types
Biotite hornfels
Rhomb Porphyry
Features
Smooth to touch
Generally rough to touch, Is one of the oldest rock, Surfaces are often shiny
Archaeological Significance
Famous Monuments
Data Not Available
Data Not Available
Sculpture
Not Yet Used
Used
Famous Sculptures
Not Applicable
Data Not Available
Pictographs
Used
Not Used
Petroglyphs
Used
Not Used
Figurines
Not Yet Used
Used
Formation
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.
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.
Mineral Content
Andalusite
Biotite, Chert, Feldspar, Garnet, Graphite, Quartz, Silica
Compound Content
Fe, Mg
Aluminium Oxide, CaO, Iron(III) Oxide, Potassium Oxide, MgO, Sodium Oxide, Silicon Dioxide, Titanium Dioxide
Types of Metamorphism
Not Applicable
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism, Hydrothermal Metamorphism, Impact Metamorphism, Regional Metamorphism
Types of Weathering
Biological Weathering
Biological Weathering, Chemical Weathering, Not Registered
Types of Erosion
Chemical Erosion, Glacier Erosion, Sea Erosion, Water Erosion, Wind Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion
Grain Size
Fine Grained
Fine Grained
Fracture
Conchoidal
Irregular
Porosity
Highly Porous
Less Porous
Compressive Strength
Not Available
Cleavage
Perfect
Imperfect
Toughness
Not Yet Found
1.7
Specific Gravity
3.4-3.9
2.5-4
Transparency
Opaque
Translucent to Opaque
Density
0.25-0.30 g/cm3
2.5-2.52 g/cm3
Specific Heat Capacity
Not Available
Resistance
Heat Resistant, Impact Resistant, Pressure Resistant
Heat Resistant, Impact Resistant
Deposits in Eastern Continents
Asia
Bangladesh, Bhutan, China, India, North Korea, Qatar, Russia, Saudi Arabia, South Korea, Thailand
China, Kazakhstan, South Korea, Thailand, Turkey, Vietnam
Africa
Cameroon, East Africa, Tanzania, 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
Not Yet Found
Greenland
Deposits in Western Continents
North America
Canada, USA
Canada, Cuba, Jamaica, USA
South America
Bolivia, Brazil, Colombia, Ecuador
Bolivia, Brazil, Colombia, Ecuador, Paraguay
Deposits in Oceania Continent
Australia
New South Wales, New Zealand, Queensland, Western Australia
New South Wales, New Zealand, Western Australia
Hornfels vs Porphyry 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. Hornfels vs Porphyry characteristics assist us to distinguish and recognize rocks. Also you can check about Properties of Hornfels and Properties of Porphyry. Learn more about Hornfels vs Porphyry in the next section. The interior uses of Hornfels include Decorative aggregates, Flooring, Homes and Interior decoration whereas the interior uses of Porphyry include Decorative aggregates and Interior decoration. Due to some exceptional properties of Hornfels and Porphyry, they have various applications in construction industry. The uses of Hornfels in construction industry include For road aggregate, Roadstone and that of Porphyry include Construction aggregate.
More about Hornfels and Porphyry
Here you can know more about Hornfels and Porphyry. The life cycle of a rock consists of formation of rock, composition of rock and transformation of rock. The composition of Hornfels and Porphyry consists of mineral content and compound content. The mineral content of Hornfels includes Andalusite and mineral content of Porphyry includes Biotite, Chert, Feldspar, Garnet, Graphite, Quartz, Silica. You can also check out the list of all Metamorphic Rocks. When we have to compare Hornfels vs Porphyry, the texture, color and appearance plays an important role in determining the type of rock. Hornfels is available in brown, dark greenish - grey, green, reddish brown colors whereas, Porphyry is available in black, brown, colourless, green, grey, red, rust, white colors. Appearance of Hornfels is Dull and that of Porphyry is Dull. Properties of rock is another aspect for Hornfels vs Porphyry. The hardness of Hornfels is 2-3 and that of Porphyry is 6-7. The types of Hornfels are Biotite hornfels whereas types of Porphyry are Rhomb Porphyry. Streak of rock is the color of powder produced when it is dragged across an unweathered surface. The streak of Hornfels is unknown while that of Porphyry is white. The specific heat capacity of Hornfels is 0.84 kJ/Kg K and that of Porphyry is Not Available. Depending on the properties like hardness, toughness, specific heat capacity, porosity etc., rocks are resistant to heat, wear, impact, etc.Hornfels is heat resistant, impact resistant, pressure resistant whereas Porphyry is heat resistant, impact resistant.
