Definition
Dacite is a volcanic igneous rock which is rintermediate in composition between andesite and rhyolite
Rhomb-porphyry is a porphyritic igneous rock with abundant wedge or lens shaped anorthoclase or feldspar phenocrysts
History
Origin
Romania and Moldova, Europe
-
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 Latin term that means purple
Class
Igneous Rocks
Igneous Rocks
Sub-Class
Durable Rock, Soft Rock
Durable Rock, Medium Hardness Rock
Family
Group
Volcanic
Volcanic
Other Categories
Fine Grained Rock, Medium Grained Rock, Opaque Rock
Fine Grained Rock, Opaque Rock
Texture
Aphanitic to Porphyritic
Aphanitic to Porphyritic
Color
Bluish - Grey, Brown, Grey, Light to Dark Grey
Black, Brown, Green, Grey, Pink, White
Maintenance
Less
Less
Durability
Durable
Durable
Water Resistant
✔
✘
✔
✘
Scratch Resistant
✔
✘
✔
✘
Stain Resistant
✔
✘
✔
✘
Wind Resistant
✔
✘
✔
✘
Acid Resistant
✔
✘
✔
✘
Appearance
Vesicular
Rough
Architecture
Interior Uses
Decorative Aggregates, Entryways, Interior Decoration
Decorative Aggregates, Homes, Interior Decoration
Exterior Uses
As Building Stone, Paving Stone, Garden Decoration
As Building Stone, As Facing Stone, Paving Stone, Garden Decoration, Office Buildings
Other Architectural Uses
Curbing
Curbing
Industry
Construction Industry
As Dimension Stone, Construction Aggregate, for Road Aggregate, Landscaping
As a Flux in the Production of Steel and Pig Iron, As a Sintering Agent in Steel Industry to process Iron Ore, As Dimension Stone, Cement Manufacture, for Road Aggregate, Making natural cement, Manufacture of Magnesium and Dolomite Refractories
Medical Industry
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-
Antiquity Uses
Artifacts
Artifacts, Monuments, Sculpture, Small Figurines
Other Uses
Commercial Uses
Commemorative Tablets, Creating Artwork
An Oil and Gas Reservoir, As a Feed Additive for Livestock, Metallurgical Flux, Soil Conditioner, Source of Magnesia (MgO)
Types
Footwall Dacite, Hanging wall Dacite, Tuff and Biotite Dacite
Igneous rock
Features
Host Rock for Lead, Is one of the oldest rock
Host Rock for Lead
Archaeological Significance
Monuments
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-
Famous Monuments
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-
Sculpture
-
-
Famous Sculptures
-
-
Pictographs
-
-
Petroglyphs
-
-
Figurines
-
-
Fossils
Absent
Absent
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.
Rhomb-porphyry is a fine-grained, hard rock which is a type of metasomatite, essentially altered basalt. It forms with or without crystallization, either below the surface as intrusive rocks or on the surface as extrusive rocks.
Composition
Mineral Content
Amphibole, Apatite, Biotite, Feldspar, Garnet, Hornblade, Magnetite, Plagioclase, Pyroxene, Quartz, Zircon
Alkali feldspar, Biotite, Plagioclase, Pyroxene
Compound Content
Ca, Fe, Potassium Oxide, Mg, Potassium, Silicon Dioxide
CaO, Cl, MgO
Transformation
Metamorphism
✔
✘
✔
✘
Types of Metamorphism
Burial Metamorphism, Cataclastic Metamorphism
Impact Metamorphism
Weathering
✔
✘
✔
✘
Types of Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Erosion
✔
✘
✔
✘
Types of Erosion
Chemical Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion, Water Erosion
Physical Properties
Hardness
2-2.255-5.5
1
7
👆🏻
Grain Size
Medium to Fine Coarse Grained
Fine Grained
Fracture
Conchoidal
Conchoidal
Streak
White
White
Porosity
Less Porous
Very Less Porous
Luster
Subvitreous to Dull
Subvitreous to Dull
Compressive Strength
70.00 N/mm2310.00 N/mm2
0.15
450
👆🏻
Cleavage
Perfect
Perfect
Toughness
-
2.7
Specific Gravity
2.86-2.872.86
0
8.4
👆🏻
Transparency
Translucent
Translucent
Density
2.77-2.771 g/cm32.8-2.9 g/cm3
0
1400
👆🏻
Thermal Properties
Specific Heat Capacity
0.92 kJ/Kg K0.92 kJ/Kg K
0.14
3.2
👆🏻
Resistance
Heat Resistant, Impact Resistant, Pressure Resistant, Wear Resistant
Heat Resistant, Pressure Resistant
Deposits in Eastern Continents
Asia
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-
Africa
-
-
Europe
France, Greece, Romania, Scotland, Spain
Bulgaria
Others
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-
Deposits in Western Continents
North America
USA
USA
South America
Argentina, Bolivia, Chile, Colombia, Ecuador, Peru, Venezuela
-
Deposits in Oceania Continent
Australia
New Zealand, South Australia, Western Australia
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