Definition
Gossan is intensely oxidized, weathered or decomposed rock, usually the upper and exposed part of an ore deposit or mineral vein.
Tephrite is an aphanitic to porphyritic textured, volcanic igneous rock
Discoverer
Cornish Gossen
Van Tooren
Etymology
From Cornish gossen from gos, blood from Old Cornish guit
From Greek tephra, ashes from Indo-European base, to burn
Class
Metamorphic Rocks
Igneous Rocks
Sub-Class
Durable Rock, Medium Hardness Rock
Durable Rock, Hard Rock
Other Categories
Fine Grained Rock, Medium Grained Rock, Opaque Rock
Coarse Grained Rock, Fine Grained Rock, Medium Grained Rock, Opaque Rock
Texture
Rough, Sandy
Aphanitic to Porphyritic
Color
Brown, Brown- Black, Gold, Green, Rust
Black, Brown, Green, Grey, White
Durability
Durable
Durable
Scratch Resistant
Yes
Yes
Appearance
Dull and Banded
Vesicular
Interior Uses
Countertops, Decorative Aggregates, Interior Decoration
Decorative Aggregates, Flooring, Homes, Interior Decoration
Exterior Uses
As Building Stone, As Facing Stone, Paving Stone, Garden Decoration, Office Buildings
As Building Stone, As Facing Stone, Garden Decoration, Office Buildings
Other Architectural Uses
Curbing
Curbing
Construction Industry
As Dimension Stone, Cement Manufacture, Construction Aggregate, for Road Aggregate
Landscaping
Antiquity Uses
Artifacts
Artifacts, Sculpture
Commercial Uses
Cemetery Markers, Commemorative Tablets, Gemstone
Production of Lime, Soil Conditioner
Types
Translocated gossan and Leakage gossan
Igneous rock
Features
Clasts are smooth to touch, Easily splits into thin plates
Host Rock for Lead
Archaeological Significance
Formation
Earth movements can cause rocks to be either deeply buried or squeezed and hence the rocks are heated and put under great pressure.
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.
Mineral Content
Apatite, Augite, Biotite, Bronzite, Calcite, Chert, Epidote, Feldspar, Hornblende, Micas, Plagioclase, Pyroxene, Quartz, Sulfides, Zircon
Alkali feldspar, Nepheline, Plagioclase, Pyroxene
Compound Content
Aluminium Oxide, CaO, Fe, FeO, Silicon Dioxide, Sulphur
CaO, Carbon Dioxide, MgO, Silicon Dioxide
Types of Metamorphism
-
Cataclastic Metamorphism, Contact Metamorphism, Impact Metamorphism, Regional Metamorphism
Types of Weathering
-
Biological Weathering, Chemical Weathering, Mechanical Weathering
Types of Erosion
Chemical Erosion, Sea Erosion, Wind Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion, Sea Erosion, Water Erosion
Grain Size
Fine to Medium Grained
Medium to Fine Coarse Grained
Fracture
Conchoidal
Uneven
Streak
White to Grey
Bluish Black
Porosity
Highly Porous
Very Less Porous
Luster
Metallic
Subvitreous to Dull
Cleavage
-
Crenulation and Pervasive
Specific Gravity
2.0
2.86
Transparency
Opaque
Opaque
Density
-9999 g/cm3
2.8-2.9 g/cm3
Resistance
Heat Resistant, Impact Resistant, Pressure Resistant
Heat Resistant, Impact Resistant
Deposits in Eastern Continents
Asia
China, India, Indonesia, Russia, Singapore, South Korea
-
Africa
Cape Verde, Ethiopia, Ghana, South Africa, Western Africa
Namibia, Uganda
Europe
Albania, France, Germany, Great Britain, United Kingdom
Germany, Hungary, Italy, Portugal, Spain
Deposits in Western Continents
North America
Canada, USA
USA
South America
Brazil, Colombia, Ecuador
-
Deposits in Oceania Continent
Australia
New South Wales, South Australia, Western Australia
New Zealand, Western Australia