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
  
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers called coal beds
  
History
  
  
Origin
New Zealand
  
USA
  
Discoverer
Unknown
  
John Peter Salley
  
Etymology
From German which means hornstone
  
From the Old English term col, which has meant mineral of fossilized carbon since the 13th century
  
Class
Metamorphic Rocks
  
Sedimentary Rocks
  
Sub-Class
Durable Rock, Soft Rock
  
Durable Rock, Soft Rock
  
Family
  
  
Group
Not Applicable
  
Not Applicable
  
Other Categories
Fine Grained Rock, Opaque Rock
  
Coarse Grained Rock, Fine Grained Rock, Medium Grained Rock, Opaque Rock
  
Texture
Granular, Platy
  
Amorphous, Glassy
  
Color
Brown, Dark Greenish - Grey, Green, Reddish Brown
  
Black, Brown, Dark Brown, Grey, Light to Dark Grey
  
Maintenance
Less
  
Less
  
Durability
Durable
  
Durable
  
Water Resistant
Yes
  
No
  
Scratch Resistant
No
  
No
  
Stain Resistant
No
  
No
  
Wind Resistant
No
  
No
  
Acid Resistant
No
  
No
  
Appearance
Dull
  
Veined or Pebbled
  
Architecture
  
  
Interior Uses
Decorative Aggregates, Flooring, Homes, Interior Decoration
  
Not Yet Used
  
Exterior Uses
As Building Stone, As Facing Stone, Garden Decoration, Office Buildings, Paving Stone
  
Not Yet Used
  
Other Architectural Uses
Curbing
  
Not Yet Used
  
Industry
  
  
Construction Industry
for Road Aggregate, Roadstone
  
Cement Manufacture, for Road Aggregate, Making natural cement, Steel Production
  
Medical Industry
Not Yet Used
  
Not Yet Used
  
Antiquity Uses
Artifacts, Monuments
  
Artifacts
  
Other Uses
  
  
Commercial Uses
Cemetery Markers, Commemorative Tablets, Creating Artwork
  
Alumina Refineries, Electricity Generation, Liquid Fuel, Manufacture of Soap, Solvents, Dyes, Plastics and Fibres, Paper Industry
  
Types
Biotite hornfels
  
Peat, Lignite, Sub-Bituminous Coal, Bituminous Coal, Anthracite, Graphite
  
Features
Smooth to touch
  
Helps in production of Heat and Electricity, Used as fossil fuel
  
Archaeological Significance
  
  
Monuments
Used
  
Not Yet Used
  
Famous Monuments
Data Not Available
  
Not Applicable
  
Sculpture
Not Yet Used
  
Not Yet Used
  
Famous Sculptures
Not Applicable
  
Not Applicable
  
Pictographs
Used
  
Not Used
  
Petroglyphs
Used
  
Not Used
  
Figurines
Not Yet Used
  
Not Yet Used
  
Fossils
Absent
  
Present
  
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.
  
Coal forms from the accumulation of plant debris in a swamp environment which is buried by sediments such as mud or sand and then compacted to form coal.
  
Composition
  
  
Mineral Content
Andalusite
  
Analcime, Apatite, Barite, Calcite, Chalcopyrite, Chlorite, Chromite, Clausthalite, Clay Minerals, Crandallite Group, Dolomite, Feldspar, Galena, Gypsum, Marcasite, Muscovite or Illite, Pyrite, Quartz, Siderite, Sphalerite, Zircon
  
Compound Content
Fe, Mg
  
Carbon, Hydrogen, Nitrogen, Oxygen, Sulphur
  
Transformation
  
  
Metamorphism
No
  
Yes
  
Types of Metamorphism
Not Applicable
  
Burial Metamorphism, Cataclastic Metamorphism, Regional Metamorphism
  
Weathering
Yes
  
No
  
Types of Weathering
Biological Weathering
  
Not Applicable
  
Erosion
Yes
  
No
  
Types of Erosion
Chemical Erosion, Glacier Erosion, Sea Erosion, Water Erosion, Wind Erosion
  
Not Applicable
  
Physical Properties
  
  
Hardness
2-3
  
1-1.5
  
Grain Size
Fine Grained
  
Medium to Fine Coarse Grained
  
Fracture
Conchoidal
  
Conchoidal
  
Streak
Unknown
  
Black
  
Porosity
Highly Porous
  
Less Porous
  
Luster
Shiny
  
Dull to Vitreous to Submetallic
  
Compressive Strength
Not Available
  
Cleavage
Perfect
  
Non-Existent
  
Toughness
Not Yet Found
  
Not Available
  
Specific Gravity
3.4-3.9
  
1.1-1.4
  
Transparency
Opaque
  
Opaque
  
Density
0.25-0.30 g/cm3
  
1100-1400 g/cm3
  
Thermal Properties
  
  
Specific Heat Capacity
0.84 kJ/Kg K
  
15
1.32 kJ/Kg K
  
4
Resistance
Heat Resistant, Impact Resistant, Pressure Resistant
  
Heat Resistant
  
Deposits in Eastern Continents
  
  
Asia
Bangladesh, Bhutan, China, India, North Korea, Qatar, Russia, Saudi Arabia, South Korea, Thailand
  
Bangladesh, Burma, Cambodia, China, India, Indonesia, Kazakhstan, Malaysia, Mongolia, Pakistan, Turkey, Vietnam
  
Africa
Cameroon, East Africa, Tanzania, Western Africa
  
Botswana, Kenya, Morocco, Mozambique, South Africa, Tanzania
  
Europe
United Kingdom
  
Belgium, Bulgaria, England, France, Germany, Greece, Hungary, Kosovo, Netherlands, Norway, Poland, Romania, Serbia, Slovakia, Slovenia, The Czech Republic, Ukraine, United Kingdom
  
Others
Not Yet Found
  
Not Yet Found
  
Deposits in Western Continents
  
  
North America
Canada, USA
  
Canada, Mexico, USA
  
South America
Bolivia, Brazil, Colombia, Ecuador
  
Brazil, Chile, Colombia, Venezuela
  
Deposits in Oceania Continent
  
  
Australia
New South Wales, New Zealand, Queensland, Western Australia
  
New South Wales, Queensland, Victoria