Hornfels and Dacite
Definition
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
Dacite is a volcanic igneous rock which is rintermediate in composition between andesite and rhyolite
History
Origin
New Zealand
Romania and Moldova, Europe
Discoverer
Unknown
Unknown
Etymology
From German which means hornstone
From Dacia, a province of the Roman Empire which lay between the Danube River and Carpathian Mountains where the rock was first described
Class
Metamorphic Rocks
Igneous Rocks
Sub-Class
Durable Rock, Soft Rock
Durable Rock, Soft Rock
Family
Group
Not Applicable
Volcanic
Other Categories
Fine Grained Rock, Opaque Rock
Fine Grained Rock, Medium Grained Rock, Opaque Rock
Texture
Texture
Granular, Platy
Aphanitic to Porphyritic
Color
Brown, Dark Greenish - Grey, Green, Reddish Brown
Bluish - Grey, 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
Vesicular
Uses
Architecture
Interior Uses
Decorative Aggregates, Flooring, Homes, Interior Decoration
Decorative Aggregates, Entryways, Interior Decoration
Exterior Uses
As Building Stone, As Facing Stone, Garden Decoration, Office Buildings, Paving Stone
As Building Stone, Paving Stone, Garden Decoration
Other Architectural Uses
Curbing
Curbing
Industry
Construction Industry
for Road Aggregate, Roadstone
As Dimension Stone, Construction Aggregate, for Road Aggregate, Landscaping
Medical Industry
Not Yet Used
Not Yet Used
Antiquity Uses
Artifacts, Monuments
Artifacts
Other Uses
Commercial Uses
Cemetery Markers, Commemorative Tablets, Creating Artwork
Commemorative Tablets, Creating Artwork
Types
Types
Biotite hornfels
Footwall Dacite, Hanging wall Dacite, Tuff and Biotite Dacite
Features
Smooth to touch
Host Rock for Lead, Is one of the oldest rock
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
Used
Petroglyphs
Used
Used
Figurines
Not Yet Used
Not Yet Used
Fossils
Absent
Absent
Formation
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.
Dacitic magma is formed by the subduction of young oceanic crust under a thick felsic continental plate. Further, the Oceanic crust is hydrothermally altered as quartz and sodium are added.
Composition
Mineral Content
Andalusite
Amphibole, Apatite, Biotite, Feldspar, Garnet, Hornblade, Magnetite, Plagioclase, Pyroxene, Quartz, Zircon
Compound Content
Fe, Mg
Ca, Fe, Potassium Oxide, Mg, Potassium, Silicon Dioxide
Transformation
Metamorphism
No
Yes
Types of Metamorphism
Not Applicable
Burial Metamorphism, Cataclastic Metamorphism
Weathering
Yes
Yes
Types of Weathering
Biological Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Erosion
Yes
Yes
Types of Erosion
Chemical Erosion, Glacier Erosion, Sea Erosion, Water Erosion, Wind Erosion
Chemical Erosion
Properties
Physical Properties
Hardness
2-3
2-2.25
Grain Size
Fine Grained
Medium to Fine Coarse Grained
Fracture
Conchoidal
Conchoidal
Streak
Unknown
White
Porosity
Highly Porous
Less Porous
Luster
Shiny
Subvitreous to Dull
Compressive Strength
5.80 N/mm2
31
Not Available
Cleavage
Perfect
Perfect
Toughness
Not Yet Found
Not Available
Specific Gravity
3.4-3.9
2.86-2.87
Transparency
Opaque
Translucent
Density
0.25-0.30 g/cm3
2.77-2.771 g/cm3
Thermal Properties
Specific Heat Capacity
0.84 kJ/Kg K
15
0.92 kJ/Kg K
10
Resistance
Heat Resistant, Impact Resistant, Pressure Resistant
Heat Resistant, Impact Resistant, Pressure Resistant, Wear Resistant
Reserves
Deposits in Eastern Continents
Asia
Bangladesh, Bhutan, China, India, North Korea, Qatar, Russia, Saudi Arabia, South Korea, Thailand
Not Yet Found
Africa
Cameroon, East Africa, Tanzania, Western Africa
Not Yet Found
Europe
United Kingdom
France, Greece, Romania, Scotland, Spain
Others
Not Yet Found
Not Yet Found
Deposits in Western Continents
North America
Canada, USA
USA
South America
Bolivia, Brazil, Colombia, Ecuador
Argentina, Bolivia, Chile, Colombia, Ecuador, Peru, Venezuela
Deposits in Oceania Continent
Australia
New South Wales, New Zealand, Queensland, Western Australia
New Zealand, South Australia, Western Australia
All about Hornfels and Dacite Properties
Know all about Hornfels and Dacite properties here. All properties of rocks are important as they define the type of rock and its application. Hornfels belongs to Metamorphic Rocks while Dacite belongs to Igneous Rocks.Texture of Hornfels is Granular, Platy whereas that of Dacite is Aphanitic to Porphyritic. Hornfels appears Dull and Dacite appears Vesicular. The luster of Hornfels is shiny while that of Dacite is subvitreous to dull. Hornfels is available in brown, dark greenish - grey, green, reddish brown colors whereas Dacite is available in bluish - grey, brown, grey, light to dark grey colors. The commercial uses of Hornfels and Dacite are cemetery markers, commemorative tablets, creating artwork.
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