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
Comendite is a hard, peralkaline igneous rock, a type of light blue grey rhyolite
History
Origin
New Zealand
Italy
Discoverer
Unknown
Unknown
Etymology
From German which means hornstone
Comendite derives its name from the area of Le Commende on San Pietro Island in Italy
Class
Metamorphic Rocks
Igneous Rocks
Sub-Class
Durable Rock, Soft Rock
Durable Rock, Hard Rock
Family
Group
-
Volcanic
Other Categories
Fine Grained Rock, Opaque Rock
Medium Grained Rock, Opaque Rock
Texture
Granular, Platy
Porphyritic
Color
Brown, Dark Greenish - Grey, Green, Reddish Brown
Blue, Bluish - Grey
Maintenance
Less
Less
Durability
Durable
Durable
Water Resistant
✔
✘
✔
✘
Scratch Resistant
✔
✘
✔
✘
Stain Resistant
✔
✘
✔
✘
Wind Resistant
✔
✘
✔
✘
Acid Resistant
✔
✘
✔
✘
Appearance
Dull
Foliated
Architecture
Interior Uses
Decorative Aggregates, Flooring, Homes, Interior Decoration
Countertops, Decorative Aggregates, Interior Decoration
Exterior Uses
As Building Stone, As Facing Stone, Garden Decoration, Office Buildings, Paving Stone
As Building Stone, As Facing Stone, Garden Decoration
Other Architectural Uses
Curbing
Curbing
Industry
Construction Industry
for Road Aggregate, Roadstone
Building houses or walls, Cement Manufacture, Construction Aggregate, for Road Aggregate, Landscaping, Making natural cement, Raw material for the manufacture of mortar
Medical Industry
-
-
Antiquity Uses
Artifacts, Monuments
Artifacts
Other Uses
Commercial Uses
Cemetery Markers, Commemorative Tablets, Creating Artwork
Cemetery Markers
Types
Biotite hornfels
Rhyolite
Features
Smooth to touch
Very fine grained rock, It is One of the Oldest, Strongest and Hardest Rock
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. Hornfels is formed from the extreme heat caused by magma or by the intense collisions and friction of tectonic plates.
Comendite is a type of Igneous rock which is formed due to cooling and solidification of lava or magma. It may form with or without crystallization, either below the surface as intrusive rocks or on the surface as extrusive rocks.
Composition
Mineral Content
Andalusite
Albite, Amphibole, Quartz
Compound Content
Fe, Mg
Al, Fe, Potassium Oxide
Transformation
Metamorphism
✔
✘
✔
✘
Types of Metamorphism
-
Cataclastic Metamorphism, Regional Metamorphism
Weathering
✔
✘
✔
✘
Types of Weathering
Biological Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Erosion
✔
✘
✔
✘
Types of Erosion
Chemical Erosion, Glacier Erosion, Sea Erosion, Water Erosion, Wind Erosion
Coastal Erosion, Water Erosion
Physical Properties
Hardness
2-36-7
1
7
👆🏻
Grain Size
Fine Grained
Medium Grained
Fracture
Conchoidal
Pervasive
Streak
-
Bluish Black
Porosity
Highly Porous
Highly Porous
Luster
Shiny
Dull
Compressive Strength
5.80 N/mm292.40 N/mm2
0.15
450
👆🏻
Cleavage
Perfect
-
Toughness
-
2
Specific Gravity
3.4-3.92.38
0
8.4
👆🏻
Transparency
Opaque
Opaque
Density
0.25-0.30 g/cm3-9999 g/cm3
0
1400
👆🏻
Thermal Properties
Specific Heat Capacity
0.84 kJ/Kg K0.79 kJ/Kg K
0.14
3.2
👆🏻
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
Africa
Cameroon, East Africa, Tanzania, Western Africa
East Africa
Europe
United Kingdom
Italy
Others
-
-
Deposits in Western Continents
North America
Canada, USA
-
South America
Bolivia, Brazil, Colombia, Ecuador
-
Deposits in Oceania Continent
Australia
New South Wales, New Zealand, Queensland, Western Australia
Queensland