Definition
Dacite is a volcanic igneous rock which is rintermediate in composition between andesite and rhyolite
Gossan is intensely oxidized, weathered or decomposed rock, usually the upper and exposed part of an ore deposit or mineral vein.
Origin
Romania and Moldova, Europe
Indonesia
Discoverer
Unknown
Cornish Gossen
Etymology
From Dacia, a province of the Roman Empire which lay between the Danube River and Carpathian Mountains where the rock was first described
From Cornish gossen from gos, blood from Old Cornish guit
Class
Igneous Rocks
Metamorphic Rocks
Sub-Class
Durable Rock, Soft Rock
Durable Rock, Medium Hardness Rock
Other Categories
Fine Grained Rock, Medium Grained Rock, Opaque Rock
Fine Grained Rock, Medium Grained Rock, Opaque Rock
Texture
Aphanitic to Porphyritic
Rough, Sandy
Color
Bluish - Grey, Brown, Grey, Light to Dark Grey
Brown, Brown- Black, Gold, Green, Rust
Durability
Durable
Durable
Appearance
Vesicular
Dull and Banded
Interior Uses
Decorative Aggregates, Entryways, Interior Decoration
Countertops, Decorative Aggregates, Interior Decoration
Exterior Uses
As Building Stone, Paving Stone, Garden Decoration
As Building Stone, As Facing Stone, Paving Stone, Garden Decoration, Office Buildings
Other Architectural Uses
Curbing
Curbing
Construction Industry
As Dimension Stone, Construction Aggregate, for Road Aggregate, Landscaping
As Dimension Stone, Cement Manufacture, Construction Aggregate, for Road Aggregate
Antiquity Uses
Artifacts
Artifacts
Commercial Uses
Commemorative Tablets, Creating Artwork
Cemetery Markers, Commemorative Tablets, Gemstone
Types
Footwall Dacite, Hanging wall Dacite, Tuff and Biotite Dacite
Translocated gossan and Leakage gossan
Features
Host Rock for Lead, Is one of the oldest rock
Clasts are smooth to touch, Easily splits into thin plates
Archaeological Significance
Formation
Dacitic magma is formed by the subduction of young oceanic crust under a thick felsic continental plate. Further, the Oceanic crust is hydrothermally altered as quartz and sodium are added.
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
Amphibole, Apatite, Biotite, Feldspar, Garnet, Hornblade, Magnetite, Plagioclase, Pyroxene, Quartz, Zircon
Apatite, Augite, Biotite, Bronzite, Calcite, Chert, Epidote, Feldspar, Hornblende, Micas, Plagioclase, Pyroxene, Quartz, Sulfides, Zircon
Compound Content
Ca, Fe, Potassium Oxide, Mg, Potassium, Silicon Dioxide
Aluminium Oxide, CaO, Fe, FeO, Silicon Dioxide, Sulphur
Types of Metamorphism
Burial Metamorphism, Cataclastic Metamorphism
-
Types of Weathering
Biological Weathering, Chemical Weathering, Mechanical Weathering
-
Types of Erosion
Chemical Erosion
Chemical Erosion, Sea Erosion, Wind Erosion
Grain Size
Medium to Fine Coarse Grained
Fine to Medium Grained
Fracture
Conchoidal
Conchoidal
Streak
White
White to Grey
Porosity
Less Porous
Highly Porous
Luster
Subvitreous to Dull
Metallic
Specific Gravity
2.86-2.87
2.0
Transparency
Translucent
Opaque
Density
2.77-2.771 g/cm3
-9999 g/cm3
Resistance
Heat Resistant, Impact Resistant, Pressure Resistant, Wear Resistant
Heat Resistant, Impact Resistant, Pressure Resistant
Deposits in Eastern Continents
Asia
-
China, India, Indonesia, Russia, Singapore, South Korea
Africa
-
Cape Verde, Ethiopia, Ghana, South Africa, Western Africa
Europe
France, Greece, Romania, Scotland, Spain
Albania, France, Germany, Great Britain, United Kingdom
Deposits in Western Continents
North America
USA
Canada, USA
South America
Argentina, Bolivia, Chile, Colombia, Ecuador, Peru, Venezuela
Brazil, Colombia, Ecuador
Deposits in Oceania Continent
Australia
New Zealand, South Australia, Western Australia
New South Wales, South Australia, Western Australia