Tephrite and Adakite
Definition
Definition
Tephrite is an aphanitic to porphyritic textured, volcanic igneous rock
Adakite is an intermediate to felsic volcanic rock that has geochemical characteristics of magma which is said to be formed by partial melting of altered basalt that is subducted below volcanic arcs
History
Origin
Germany
Adak, Aleutian Islands
Discoverer
Van Tooren
Defant and Drummond
Etymology
From Greek tephra, ashes from Indo-European base, to burn
From Adak, Aleutian Islands
Class
Igneous Rocks
Igneous Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Medium Hardness Rock
Family
Group
Volcanic
Volcanic
Other Categories
Coarse Grained Rock, Fine Grained Rock, Medium Grained Rock, Opaque Rock
Fine Grained Rock, Medium Grained Rock, Opaque Rock
Texture
Texture
Aphanitic to Porphyritic
Porphyritic
Color
Black, Brown, Colourless, Green, Grey, White
Black, Brown, Light to Dark Grey
Maintenance
Less
Less
Durability
Durable
Durable
Water Resistant
Yes
No
Scratch Resistant
Yes
No
Stain Resistant
No
No
Wind Resistant
Yes
Yes
Acid Resistant
No
Yes
Appearance
Vesicular
Dull and Soft
Uses
Architecture
Interior Uses
Decorative Aggregates, Flooring, Homes, Interior Decoration
Decorative Aggregates, Floor Tiles, Homes, Hotels, Kitchens
Exterior Uses
As Building Stone, As Facing Stone, Garden Decoration, Office Buildings
As Building Stone, As Facing Stone, Office Buildings
Other Architectural Uses
Curbing
Whetstones
Industry
Construction Industry
Landscaping
As Dimension Stone, Cobblestones, Rail Track Ballast, Roadstone
Medical Industry
Not Yet Used
Not Yet Used
Antiquity Uses
Artifacts, Sculpture
Monuments, Sculpture, Small Figurines
Other Uses
Commercial Uses
Production of Lime, Soil Conditioner
Commemorative Tablets, Pottery, Used in aquariums
Types
Types
Not Available
Not Available
Features
Host Rock for Lead
Has High structural resistance against erosion and climate, Host rock for Diamond, Very fine grained rock
Archaeological Significance
Monuments
Not Yet Used
Used
Famous Monuments
Not Applicable
Data Not Available
Sculpture
Used
Used
Famous Sculptures
Data Not Available
Data Not Available
Pictographs
Not Used
Used
Petroglyphs
Not Used
Used
Figurines
Used
Used
Fossils
Absent
Absent
Formation
Formation
Tephrite 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.
Adakite rocks are formed when the hydrous fluids are released from minerals that break down in metamorphosed basalt, and rise into the mantle they initiate partial melting.
Composition
Mineral Content
Alkali feldspar, Nepheline, Plagioclase, Pyroxene
Olivine, Plagioclase, Pyroxene
Compound Content
CaO, Carbon Dioxide, MgO, Silicon Dioxide
Aluminium Oxide, MgO, Silicon Dioxide
Transformation
Metamorphism
Yes
Yes
Types of Metamorphism
Cataclastic Metamorphism, Contact Metamorphism, Impact Metamorphism, Regional Metamorphism
Cataclastic Metamorphism, Contact Metamorphism, Impact Metamorphism, Regional Metamorphism
Weathering
Yes
Yes
Types of Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
Chemical Weathering, Mechanical Weathering
Erosion
Yes
Yes
Types of Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion, Sea Erosion, Water Erosion
Coastal Erosion, Sea Erosion, Water Erosion
Properties
Physical Properties
Hardness
6.5
3-4
Grain Size
Medium to Fine Coarse Grained
Fine to Medium Grained
Fracture
Uneven
Conchoidal
Streak
Bluish Black
Bluish Black
Porosity
Very Less Porous
Less Porous
Luster
Subvitreous to Dull
Grainy, Pearly and Vitreous
Compressive Strength
90.00 N/mm2
22
Not Available
Cleavage
Crenulation and Pervasive
Not Available
Toughness
2.4
Not Available
Specific Gravity
2.86
Not Available
Transparency
Opaque
Opaque
Density
2.8-2.9 g/cm3
Not Available
Thermal Properties
Specific Heat Capacity
0.92 kJ/Kg K
10
Not Available
Resistance
Heat Resistant, Impact Resistant
Heat Resistant, Pressure Resistant, Wear Resistant
Reserves
Deposits in Eastern Continents
Asia
Not Yet Found
India, Russia
Africa
Namibia, Uganda
Ethiopia, Somalia, South Africa
Europe
Germany, Hungary, Italy, Portugal, Spain
Iceland
Others
Not Yet Found
Not Yet Found
Deposits in Western Continents
North America
USA
Canada, USA
South America
Not Yet Found
Brazil
Deposits in Oceania Continent
Australia
New Zealand, Western Australia
Not Yet Found
All about Tephrite and Adakite Properties
Know all about Tephrite and Adakite properties here. All properties of rocks are important as they define the type of rock and its application. Tephrite and Adakite belong to Igneous Rocks.Texture of Tephrite is Aphanitic to Porphyritic whereas that of Adakite is Porphyritic. Tephrite appears Vesicular and Adakite appears Dull and Soft. The luster of Tephrite is subvitreous to dull while that of Adakite is grainy, pearly and vitreous. Tephrite is available in black, brown, colourless, green, grey, white colors whereas Adakite is available in black, brown, light to dark grey colors. The commercial uses of Tephrite are production of lime, soil conditioner and that of Adakite are commemorative tablets, pottery, used in aquariums.
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