Tuff and Variolite
Definition
Definition
Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption
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
History
Origin
Italy
France
Discoverer
Unknown
Unknown
Etymology
From a Latin word tophous then in Italian tufo and finally tuff
From Latin varius, speckled, variegated
Class
Igneous Rocks
Igneous Rocks
Sub-Class
Durable Rock, Medium Hardness Rock
Durable Rock, Hard Rock
Family
Group
Volcanic
Volcanic
Other Categories
Fine Grained Rock, Opaque Rock
Opaque Rock
Texture
Texture
Clastic, Pyroclastic
Glassy, Massive, Porphyritic, Scoriaceous, Vesicular
Color
Brown, Grey, Yellow
Black, Brown, Light to Dark Grey
Maintenance
More
Less
Durability
Durable
Durable
Water Resistant
Yes
Yes
Scratch Resistant
Yes
Yes
Stain Resistant
No
No
Wind Resistant
No
No
Acid Resistant
No
Yes
Appearance
Dull, Vesicular and Foilated
Dull and Soft
Uses
Architecture
Interior Uses
Decorative Aggregates, Entryways, Flooring, Homes, Interior Decoration
Floor Tiles, Flooring, Homes, Hotels, Kitchens
Exterior Uses
As Building Stone, As Facing Stone, Garden Decoration, Office Buildings, Paving Stone
Garden Decoration, Office Buildings
Other Architectural Uses
Curbing
Curbing
Industry
Construction Industry
Building houses or walls, Construction Aggregate
As Dimension Stone, Cobblestones, Rail Track Ballast, Roadstone
Medical Industry
Not Yet Used
Not Yet Used
Antiquity Uses
Artifacts, Monuments, Sculpture, Small Figurines
Artifacts, Monuments, Sculpture
Other Uses
Commercial Uses
Creating Artwork
Cemetery Markers, Creating Artwork
Types
Types
Welded tuff, Rhyolitic tuff, Basaltic tuff, Trachyte tuff, Andesitic tuff and Ignimbrite.
Not Available
Features
Always found as volcanic pipes over deep continental crust
Has High structural resistance against erosion and climate, Very fine grained rock
Archaeological Significance
Monuments
Used
Used
Famous Monuments
Easter Island in the Polynesian Triangle, Pacific Ocean
Data Not Available
Sculpture
Used
Used
Famous Sculptures
Data Not Available
Data Not Available
Pictographs
Used
Used
Petroglyphs
Used
Used
Figurines
Used
Used
Fossils
Absent
Absent
Formation
Formation
Tuff is formed when large masses of ash and sand which are mixed with hot gases are ejected by a volcano and avalanche rapidly down its slopes.
Variolites are a group of dark green basic igneous rocks that exhibit pale colored spots on weathered surfaces that give them a pockmarked appearance.
Composition
Mineral Content
Calcite, Chlorite
Olivine, Plagioclase, Pyroxene
Compound Content
Hydrogen Sulfide, Sulfur Dioxide
Aluminium Oxide, CaO, Iron(III) Oxide, FeO, Potassium Oxide, MgO, MnO, Sodium Oxide, Phosphorus Pentoxide, Silicon Dioxide, Titanium Dioxide
Transformation
Metamorphism
Yes
Yes
Types of Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism, Hydrothermal Metamorphism, Impact Metamorphism, Regional Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism, Hydrothermal Metamorphism, Impact Metamorphism, Regional Metamorphism
Weathering
Yes
Yes
Types of Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Erosion
Yes
No
Types of Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion, Sea Erosion, Water Erosion, Wind Erosion
Not Applicable
Properties
Physical Properties
Hardness
4-6
6
Grain Size
Fine Grained
Not Applicable
Fracture
Uneven
Conchoidal
Streak
White
White to Grey
Porosity
Highly Porous
Less Porous
Luster
Vitreous to Dull
Not Available
Compressive Strength
243.80 N/mm2
5
37.50 N/mm2
27
Cleavage
Not Available
Not Available
Toughness
Not Available
2.3
Specific Gravity
2.73
2.8-3
Transparency
Opaque
Opaque
Density
1-1.8 g/cm3
2.9-3.1 g/cm3
Thermal Properties
Specific Heat Capacity
0.20 kJ/Kg K
25
0.84 kJ/Kg K
15
Resistance
Heat Resistant, Impact Resistant, Pressure Resistant, Wear Resistant
Heat Resistant, Pressure Resistant, Wear Resistant
Reserves
Deposits in Eastern Continents
Asia
Afghanistan, Armenia, Azerbaijan, Burma, Cambodia, China, India, Indonesia, Iran, Japan, Malaysia, Mongolia, Nepal, North Korea, Pakistan, Saudi Arabia, Syria, Taiwan, Thailand, Turkey, Vietnam, Yemen
India, Russia
Africa
Cameroon, Cape Verde, Eritrea, Ethiopia, Kenya, Libya, Madagascar, Nigeria, Rwanda, South Africa, Sudan, Uganda
South Africa
Europe
France, Georgia, Germany, Greece, Iceland, Italy, Netherlands, Poland, Portugal, Spain, United Kingdom
Iceland
Others
Antarctica, Hawaii Islands
Not Yet Found
Deposits in Western Continents
North America
Canada, Costa Rica, Panama, USA
Canada, USA
South America
Argentina, Bolivia, Brazil, Chile, Ecuador, Paraguay
Brazil
Deposits in Oceania Continent
Australia
Central Australia, Western Australia
Not Yet Found
All about Tuff and Variolite Properties
Know all about Tuff and Variolite properties here. All properties of rocks are important as they define the type of rock and its application. Tuff and Variolite belong to Igneous Rocks.Texture of Tuff is Clastic, Pyroclastic whereas that of Variolite is Glassy, Massive, Porphyritic, Scoriaceous, Vesicular. Tuff appears Dull, Vesicular and Foilated and Variolite appears Dull and Soft. The luster of Tuff is vitreous to dull while that of Variolite is not available. Tuff is available in brown, grey, yellow colors whereas Variolite is available in black, brown, light to dark grey colors. The commercial uses of Tuff are creating artwork and that of Variolite are cemetery markers, creating artwork.
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