Definition
Rhyodacite is an extrusive volcanic rock intermediate in composition between dacite and rhyolite
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
USA
USA, Australia
Discoverer
Unknown
Tornebohm
Etymology
Rhyo lite + dacite : a rock intermediate between rhyolite and dacite that is the extrusive equivalent of granodiorite
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, Medium Hardness Rock
Durable Rock, Hard Rock
Group
Volcanic
Not Applicable
Other Categories
Fine Grained Rock, Opaque Rock
Fine Grained Rock, Opaque Rock
Texture
Earthy
Earthy, Mud-rich, Rough
Color
Black to Grey, Dark Greenish - Grey
Black, Brown, Colourless, Green, Grey, White
Durability
Durable
Durable
Scratch Resistant
Yes
Yes
Interior Uses
Decorative Aggregates, Interior Decoration
Decorative Aggregates, Entryways, Interior Decoration
Exterior Uses
As Building Stone, Garden Decoration
As Building Stone, As Facing Stone, Garden Decoration, Paving Stone
Other Architectural Uses
Curbing
Curbing
Construction Industry
As Dimension Stone, Construction Aggregate, for Road Aggregate, 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
Medical Industry
Not Yet Used
Not Applicable
Antiquity Uses
Artifacts
Artifacts, Monuments, Sculpture
Commercial Uses
Cemetery Markers, Creating Artwork
Creating Artwork, Gemstone, Jewelry, Metallurgical Flux, Source of Magnesia (MgO)
Types
Not Available
Endoskarns
Features
Available in Lots of Colors and Patterns
Host Rock for Lead, Zinc and Copper Deposits
Archaeological Significance
Monuments
Not Yet Used
Used
Famous Monuments
Not Applicable
Data Not Available
Sculpture
Not Yet Used
Used
Famous Sculptures
Not Applicable
Data Not Available
Pictographs
Used
Not Used
Petroglyphs
Used
Not Used
Figurines
Not Yet Used
Used
Formation
Rhyodacite 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
Amphibole, Apatite, Biotite, Feldspar, Garnet, Hornblade, Magnetite, Plagioclase, Pyroxene, Quartz, Zircon
Calcite, Enstatite, Epidote, Garnet, Magnetite, Pyroxene, Titanite
Compound Content
Ca, Fe, Potassium Oxide, NA, Potassium, Silicon Dioxide
Au, CaO, Carbon Dioxide, Cu, Fe, MgO
Types of Metamorphism
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism, Hydrothermal 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
Not Applicable
Types of Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion
Not Applicable
Grain Size
Fine Grained
Fine Grained
Fracture
Conchoidal
Irregular
Streak
Black
Light to dark brown
Porosity
Less Porous
Less Porous
Luster
Greasy to Dull
Waxy and Dull
Compressive Strength
Not Available
Cleavage
Not Available
Slaty
Specific Gravity
2.34-2.40
2.86
Transparency
Opaque
Opaque
Density
Not Available
2.8-2.9 g/cm3
Resistance
Heat Resistant
Heat Resistant
Deposits in Eastern Continents
Asia
China, India, Iran, Saudi Arabia, Sri Lanka, Taiwan, Thailand, Turkey, Vietnam
China, India, Russia, Saudi Arabia, South Korea, Sri Lanka
Africa
Angola, Egypt, Madagascar, Namibia, Nigeria, South Africa
South Africa, Western Africa
Europe
Austria, Belgium, Finland, France, Germany, Italy, Norway, Sardinia, Spain, Switzerland
United Kingdom
Others
Not Yet Found
Not Yet Found
Deposits in Western Continents
North America
Canada, USA
Canada
South America
Not Yet Found
Brazil, Colombia, Paraguay
Deposits in Oceania Continent
Australia
Not Yet Found
Central Australia, Western Australia