Definition
Trachyte is a grey fine-grained volcanic rock which mainly consists of alkali feldspar
Gossan is intensely oxidized, weathered or decomposed rock, usually the upper and exposed part of an ore deposit or mineral vein.
Discoverer
Alexandre Brongniart and René Just Haüy
Cornish Gossen
Etymology
From Greek trakhus rough’ or trakhutēs roughness
From Cornish gossen from gos, blood from Old Cornish guit
Class
Igneous Rocks
Metamorphic Rocks
Sub-Class
Durable Rock, Medium Hardness Rock
Durable Rock, Medium Hardness Rock
Other Categories
Fine Grained Rock, Opaque Rock
Fine Grained Rock, Medium Grained Rock, Opaque Rock
Texture
Aphanitic to Porphyritic
Rough, Sandy
Color
Black, Brown, Dark Greenish - Grey, Green, Grey, Light to Dark Grey, White
Brown, Brown- Black, Gold, Green, Rust
Durability
Durable
Durable
Scratch Resistant
Yes
Yes
Appearance
Banded
Dull and Banded
Interior Uses
Decorative Aggregates, Flooring, Homes, Interior Decoration
Countertops, Decorative Aggregates, Interior Decoration
Exterior Uses
As Building Stone, As Facing Stone, Paving Stone, Garden Decoration, Office Buildings
As Building Stone, As Facing Stone, Paving Stone, Garden Decoration, Office Buildings
Other Architectural Uses
Curbing
Curbing
Construction Industry
As Dimension Stone, Building houses or walls, Cement Manufacture, Construction Aggregate, for Road Aggregate, Landscaping, Making natural cement, Manufacture of Magnesium and Dolomite Refractories
As Dimension Stone, Cement Manufacture, Construction Aggregate, for Road Aggregate
Antiquity Uses
Artifacts, Monuments, Sculpture, Small Figurines
Artifacts
Commercial Uses
Cemetery Markers, Creating Artwork
Cemetery Markers, Commemorative Tablets, Gemstone
Types
Felsic volcanic rock
Translocated gossan and Leakage gossan
Features
Available in Lots of Colors and Patterns, Is one of the oldest rock, Matrix variable
Clasts are smooth to touch, Easily splits into thin plates
Archaeological Significance
Formation
Trachyte is an igneous volcanic rock with an aphanitic to porphyritic texture. It is the volcanic equivalent of syenite rock and forms as a result of magmatic differentiation.
Earth movements can cause rocks to be either deeply buried or squeezed and hence the rocks are heated and put under great pressure.
Mineral Content
Augite, Biotite, Feldspar, Hornblade, Plagioclase, Quartz
Apatite, Augite, Biotite, Bronzite, Calcite, Chert, Epidote, Feldspar, Hornblende, Micas, Plagioclase, Pyroxene, Quartz, Sulfides, Zircon
Compound Content
Potassium Oxide, Sodium Oxide, Silicon Dioxide
Aluminium Oxide, CaO, Fe, FeO, Silicon Dioxide, Sulphur
Types of Metamorphism
Cataclastic Metamorphism, Contact Metamorphism, Regional Metamorphism
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Types of Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
-
Types of Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion, Sea Erosion, Water Erosion, Wind Erosion
Chemical Erosion, Sea Erosion, Wind Erosion
Grain Size
Fine Grained
Fine to Medium Grained
Streak
White
White to Grey
Porosity
Less Porous
Highly Porous
Transparency
Opaque
Opaque
Density
2.43-2.45 g/cm3
-9999 g/cm3
Resistance
Heat Resistant, Impact Resistant, Wear Resistant
Heat Resistant, Impact Resistant, Pressure Resistant
Deposits in Eastern Continents
Asia
China, India, Iran, Saudi Arabia, Sri Lanka, Taiwan, Thailand, Turkey, Vietnam
China, India, Indonesia, Russia, Singapore, South Korea
Africa
Angola, Egypt, Madagascar, Namibia, Nigeria, South Africa
Cape Verde, Ethiopia, Ghana, South Africa, Western Africa
Europe
Bulgaria, England, Germany, Norway, Romania, Switzerland
Albania, France, Germany, Great Britain, United Kingdom
Deposits in Western Continents
North America
USA
Canada, USA
South America
Brazil, Chile
Brazil, Colombia, Ecuador
Deposits in Oceania Continent
Australia
New Zealand, Queensland, South Australia, Western Australia
New South Wales, South Australia, Western Australia