Dacite and Mylonite
Definition
Definition
Dacite is a volcanic igneous rock which is rintermediate in composition between andesite and rhyolite
Mylonite is a metamorphic rock formed by ductile deformation during intense shearing encountered during folding and faulting, a process termed cataclastic or dynamic metamorphism
History
Origin
Romania and Moldova, Europe
New Zealand
Discoverer
Unknown
Unknown
Etymology
From Dacia, a province of the Roman Empire which lay between the Danube River and Carpathian Mountains where the rock was first described
From Greek mulōn mill + -ite
Class
Igneous Rocks
Metamorphic Rocks
Sub-Class
Durable Rock, Soft Rock
Durable Rock, Medium Hardness Rock
Family
Group
Volcanic
Not Applicable
Other Categories
Fine Grained Rock, Medium Grained Rock, Opaque Rock
Fine Grained Rock, Opaque Rock
Texture
Texture
Aphanitic to Porphyritic
Foliated
Color
Bluish - Grey, Brown, Grey, Light to Dark Grey
Black to Grey
Maintenance
Less
Less
Durability
Durable
Durable
Water Resistant
No
Yes
Scratch Resistant
No
Yes
Stain Resistant
No
No
Wind Resistant
No
No
Acid Resistant
No
No
Appearance
Vesicular
Dull, Banded and Foilated
Uses
Architecture
Interior Uses
Decorative Aggregates, Entryways, Interior Decoration
Decorative Aggregates, Interior Decoration
Exterior Uses
As Building Stone, Paving Stone, Garden Decoration
As Building Stone, As Facing Stone, Paving Stone, Garden Decoration
Other Architectural Uses
Curbing
Curbing
Industry
Construction Industry
As Dimension Stone, Construction Aggregate, for Road Aggregate, Landscaping
for Road Aggregate, Landscaping, Roadstone
Medical Industry
Not Yet Used
Not Yet Used
Antiquity Uses
Artifacts
Artifacts, Monuments
Other Uses
Commercial Uses
Commemorative Tablets, Creating Artwork
Creating Artwork, Gemstone, Jewelry
Types
Types
Footwall Dacite, Hanging wall Dacite, Tuff and Biotite Dacite
Blastomylonites, Ultramylonites and Phyllonites
Features
Host Rock for Lead, Is one of the oldest rock
Surfaces are often shiny
Archaeological Significance
Monuments
Not Yet Used
Used
Famous Monuments
Not Applicable
Data Not Available
Sculpture
Not Yet Used
Used
Famous Sculptures
Not Applicable
Data Not Available
Pictographs
Used
Used
Petroglyphs
Used
Used
Figurines
Not Yet Used
Used
Fossils
Absent
Absent
Formation
Formation
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.
Mylonites are ductilely deformed rocks formed by the accumulation of large shear strain, in ductile fault zones.
Composition
Mineral Content
Amphibole, Apatite, Biotite, Feldspar, Garnet, Hornblade, Magnetite, Plagioclase, Pyroxene, Quartz, Zircon
Porphyroblasts
Compound Content
Ca, Fe, Potassium Oxide, Mg, Potassium, Silicon Dioxide
Aluminium Oxide, Calcium Sulfate, Chromium(III) Oxide, Iron(III) Oxide, Magnesium Carbonate, Silicon Dioxide
Transformation
Metamorphism
Yes
No
Types of Metamorphism
Burial Metamorphism, Cataclastic Metamorphism
Not Applicable
Weathering
Yes
Yes
Types of Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Erosion
Yes
Yes
Types of Erosion
Chemical Erosion
Chemical Erosion, Sea Erosion, Wind Erosion
Properties
Physical Properties
Hardness
2-2.25
3-4
Grain Size
Medium to Fine Coarse Grained
Fine Grained
Fracture
Conchoidal
Conchoidal
Streak
White
White
Porosity
Less Porous
Highly Porous
Luster
Subvitreous to Dull
Shiny
Compressive Strength
Not Available
1.28 N/mm2
32
Cleavage
Perfect
Conchoidal
Toughness
Not Available
Not Available
Specific Gravity
2.86-2.87
2.97-3.05
Transparency
Translucent
Opaque
Density
2.77-2.771 g/cm3
2.6-4.8 g/cm3
Thermal Properties
Specific Heat Capacity
0.92 kJ/Kg K
10
1.50 kJ/Kg K
3
Resistance
Heat Resistant, Impact Resistant, Pressure Resistant, Wear Resistant
Heat Resistant, Impact Resistant, Pressure Resistant
Reserves
Deposits in Eastern Continents
Asia
Not Yet Found
China, India, Indonesia, Saudi Arabia, South Korea
Africa
Not Yet Found
Eritrea, Ethiopia, Ghana, South Africa, Western Africa
Europe
France, Greece, Romania, Scotland, Spain
England, Finland, France, Germany, Great Britain, Greece, United Kingdom
Others
Not Yet Found
Not Yet Found
Deposits in Western Continents
North America
USA
USA
South America
Argentina, Bolivia, Chile, Colombia, Ecuador, Peru, Venezuela
Not Yet Found
Deposits in Oceania Continent
Australia
New Zealand, South Australia, Western Australia
Central Australia, Western Australia
All about Dacite and Mylonite Properties
Know all about Dacite and Mylonite properties here. All properties of rocks are important as they define the type of rock and its application. Dacite belongs to Igneous Rocks while Mylonite belongs to Metamorphic Rocks.Texture of Dacite is Aphanitic to Porphyritic whereas that of Mylonite is Foliated. Dacite appears Vesicular and Mylonite appears Dull, Banded and Foilated. The luster of Dacite is subvitreous to dull while that of Mylonite is shiny. Dacite is available in bluish - grey, brown, grey, light to dark grey colors whereas Mylonite is available in black to grey colors. The commercial uses of Dacite are commemorative tablets, creating artwork and that of Mylonite are creating artwork, gemstone, jewelry.
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