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Variolite and Dacite


Dacite and Variolite


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   

Summary >>
<< Reserves

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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