Variolite and Dacite
Definition
Definition
Variolites are a group of dark green basic igneous rocks which exhibit pale colored spots, or spherules, especially on weathered surfaces, that give them a pockmarked appearance
Dacite is a volcanic igneous rock which is rintermediate in composition between andesite and rhyolite
History
Origin
France
Romania and Moldova, Europe
Discoverer
Unknown
Unknown
Etymology
From Latin varius, speckled, variegated
From Dacia, a province of the Roman Empire which lay between the Danube River and Carpathian Mountains where the rock was first described
Class
Igneous Rocks
Igneous Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Soft Rock
Family
Group
Volcanic
Volcanic
Other Categories
Opaque Rock
Fine Grained Rock, Medium Grained Rock, Opaque Rock
Texture
Texture
Glassy, Massive, Porphyritic, Scoriaceous, Vesicular
Aphanitic to Porphyritic
Color
Black, Brown, Light to Dark Grey
Bluish - Grey, Brown, Grey, Light to Dark Grey
Maintenance
Less
Less
Durability
Durable
Durable
Water Resistant
Yes
No
Scratch Resistant
Yes
No
Stain Resistant
No
No
Wind Resistant
No
No
Acid Resistant
Yes
No
Appearance
Dull and Soft
Vesicular
Uses
Architecture
Interior Uses
Floor Tiles, Flooring, Homes, Hotels, Kitchens
Decorative Aggregates, Entryways, Interior Decoration
Exterior Uses
Garden Decoration, Office Buildings
As Building Stone, Paving Stone, Garden Decoration
Other Architectural Uses
Curbing
Curbing
Industry
Construction Industry
As Dimension Stone, Cobblestones, Rail Track Ballast, Roadstone
As Dimension Stone, Construction Aggregate, for Road Aggregate, Landscaping
Medical Industry
Not Yet Used
Not Yet Used
Antiquity Uses
Artifacts, Monuments, Sculpture
Artifacts
Other Uses
Commercial Uses
Cemetery Markers, Creating Artwork
Commemorative Tablets, Creating Artwork
Types
Types
Not Available
Footwall Dacite, Hanging wall Dacite, Tuff and Biotite Dacite
Features
Has High structural resistance against erosion and climate, Very fine grained rock
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
Used
Not Yet Used
Famous Sculptures
Data Not Available
Not Applicable
Pictographs
Used
Used
Petroglyphs
Used
Used
Figurines
Used
Not Yet Used
Fossils
Absent
Absent
Formation
Formation
Variolites are a group of dark green basic igneous rocks that exhibit pale colored spots on weathered surfaces that give them a pockmarked appearance.
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
Olivine, Plagioclase, Pyroxene
Amphibole, Apatite, Biotite, Feldspar, Garnet, Hornblade, Magnetite, Plagioclase, Pyroxene, Quartz, Zircon
Compound Content
Aluminium Oxide, CaO, Iron(III) Oxide, FeO, Potassium Oxide, MgO, MnO, Sodium Oxide, Phosphorus Pentoxide, Silicon Dioxide, Titanium Dioxide
Ca, Fe, Potassium Oxide, Mg, Potassium, Silicon Dioxide
Transformation
Metamorphism
Yes
Yes
Types of Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism, Hydrothermal Metamorphism, Impact Metamorphism, Regional Metamorphism
Burial Metamorphism, Cataclastic Metamorphism
Weathering
Yes
Yes
Types of Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Erosion
No
Yes
Types of Erosion
Not Applicable
Chemical Erosion
Properties
Physical Properties
Hardness
6
2-2.25
Grain Size
Not Applicable
Medium to Fine Coarse Grained
Fracture
Conchoidal
Conchoidal
Streak
White to Grey
White
Porosity
Less Porous
Less Porous
Luster
Not Available
Subvitreous to Dull
Compressive Strength
37.50 N/mm2
27
Not Available
Cleavage
Not Available
Perfect
Toughness
2.3
Not Available
Specific Gravity
2.8-3
2.86-2.87
Transparency
Opaque
Translucent
Density
2.9-3.1 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, Pressure Resistant, Wear Resistant
Heat Resistant, Impact Resistant, Pressure Resistant, Wear Resistant
Reserves
Deposits in Eastern Continents
Asia
India, Russia
Not Yet Found
Africa
South Africa
Not Yet Found
Europe
Iceland
France, Greece, Romania, Scotland, Spain
Others
Not Yet Found
Not Yet Found
Deposits in Western Continents
North America
Canada, USA
USA
South America
Brazil
Argentina, Bolivia, Chile, Colombia, Ecuador, Peru, Venezuela
Deposits in Oceania Continent
Australia
Not Yet Found
New Zealand, South Australia, Western Australia
All about Variolite and Dacite Properties
Know all about Variolite and Dacite properties here. All properties of rocks are important as they define the type of rock and its application. Variolite and Dacite belong to Igneous Rocks.Texture of Variolite is Glassy, Massive, Porphyritic, Scoriaceous, Vesicular whereas that of Dacite is Aphanitic to Porphyritic. Variolite appears Dull and Soft and Dacite appears Vesicular. The luster of Variolite is not available while that of Dacite is subvitreous to dull. Variolite is available in black, brown, light to dark grey colors whereas Dacite is available in bluish - grey, brown, grey, light to dark grey colors. The commercial uses of Variolite are cemetery markers, creating artwork and that of Dacite are commemorative tablets, creating artwork.
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