Definition
Tephrite is an aphanitic to porphyritic textured, volcanic igneous rock
Skarns are formed during regional or contact metamorphism and from a variety of metasomatic processes involving fluids of magmatic, metamorphic, and/or marine origin
Origin
Germany
USA, Australia
Discoverer
Van Tooren
Tornebohm
Etymology
From Greek tephra, ashes from Indo-European base, to burn
From an old Swedish mining term originally used to describe a type of silicate gangue or waste rock.
Class
Igneous Rocks
Metamorphic Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Hard Rock
Other Categories
Coarse Grained Rock, Fine Grained Rock, Medium Grained Rock, Opaque Rock
Fine Grained Rock, Opaque Rock
Texture
Aphanitic to Porphyritic
Earthy, Mud-rich, Rough
Color
Black, Brown, Green, Grey, White
Black, Brown, Green, Grey, White
Durability
Durable
Durable
Scratch Resistant
Yes
Yes
Appearance
Vesicular
Dull
Interior Uses
Decorative Aggregates, Flooring, Homes, Interior Decoration
Decorative Aggregates, Entryways, Interior Decoration
Exterior Uses
As Building Stone, As Facing Stone, Garden Decoration, Office Buildings
As Building Stone, As Facing Stone, Garden Decoration, Paving Stone
Other Architectural Uses
Curbing
Curbing
Construction Industry
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, Gold and Silver production, Manufacture of Magnesium and Dolomite Refractories
Antiquity Uses
Artifacts, Sculpture
Artifacts, Monuments, Sculpture
Commercial Uses
Production of Lime, Soil Conditioner
Creating Artwork, Gemstone, Jewelry, Metallurgical Flux, Source of Magnesia (MgO)
Types
Igneous rock
Endoskarns
Features
Host Rock for Lead
Host Rock for Lead, Zinc and Copper Deposits
Archaeological Significance
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.
Due to change in environmental conditions, rocks are heated and pressurized deep inside the Earth's surface. Skarn is formed from the extreme heat caused by magma or by the intense collisions and friction of tectonic plates.
Mineral Content
Alkali feldspar, Nepheline, Plagioclase, Pyroxene
Calcite, Enstatite, Epidote, Garnet, Magnetite, Pyroxene, Titanite
Compound Content
CaO, Carbon Dioxide, MgO, Silicon Dioxide
Au, CaO, Carbon Dioxide, Cu, Fe, MgO
Types of Metamorphism
Cataclastic Metamorphism, Contact Metamorphism, Impact Metamorphism, Regional Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism, Hydrothermal Metamorphism, Impact Metamorphism, Regional Metamorphism
Types of Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
-
Types of Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion, Sea Erosion, Water Erosion
-
Grain Size
Medium to Fine Coarse Grained
Fine Grained
Fracture
Uneven
Irregular
Streak
Bluish Black
Light to dark brown
Porosity
Very Less Porous
Less Porous
Luster
Subvitreous to Dull
Waxy and Dull
Cleavage
Crenulation and Pervasive
Slaty
Specific Gravity
2.86
2.86
Transparency
Opaque
Opaque
Density
2.8-2.9 g/cm3
2.8-2.9 g/cm3
Resistance
Heat Resistant, Impact Resistant
Heat Resistant
Deposits in Eastern Continents
Asia
-
China, India, Russia, Saudi Arabia, South Korea, Sri Lanka
Africa
Namibia, Uganda
South Africa, Western Africa
Europe
Germany, Hungary, Italy, Portugal, Spain
United Kingdom
Deposits in Western Continents
South America
-
Brazil, Colombia, Paraguay
Deposits in Oceania Continent
Australia
New Zealand, Western Australia
Central Australia, Western Australia