Definition
Banded iron formation are distinctive units of sedimentary rock that are almost always of Precambrian age
Porphyry is a reddish-brown to purple igneous rock containing large phenocrysts of various minerals embedded in a fine-grained matrix
Origin
Western Australia, Minnesota
Egypt
Discoverer
Unknown
Unknown
Etymology
From its formation process
From Old French porfire, from Italian porfiro and in some cases directly from Latin porphyrites
Class
Sedimentary Rocks
Igneous Rocks
Sub-Class
Durable Rock, Medium Hardness Rock
Durable Rock, Hard Rock
Group
Not Applicable
Plutonic
Other Categories
Coarse Grained Rock, Opaque Rock
Fine Grained Rock, Opaque Rock
Texture
Banded, Trellis
Porphyritic
Color
Red, Reddish Brown
Black, Brown, Colourless, Green, Grey, Red, Rust, White
Durability
Durable
Durable
Scratch Resistant
Yes
Yes
Appearance
Layered, Banded, Veined and Shiny
Dull
Interior Uses
Decorative Aggregates, Homes
Decorative Aggregates, Interior Decoration
Exterior Uses
Paving Stone, Office Buildings
Garden Decoration, Paving Stone
Other Architectural Uses
Curbing, Whetstones
Curbing
Construction Industry
As Dimension Stone, Used for flooring, stair treads, borders and window sills.
Construction Aggregate
Medical Industry
Not Yet Used
Not Yet Used
Antiquity Uses
Artifacts
Artifacts, Monuments, Sculpture
Commercial Uses
As a touchstone, Cemetery Markers, Creating Artwork
Creating Artwork, Gemstone, Jewelry
Types
Algoma-type , Lake Superior-type, Superior-type and Taconite
Rhomb Porphyry
Features
Is one of the oldest rock
Generally rough to touch, Is one of the oldest rock, Surfaces are often shiny
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
Not Used
Not Used
Petroglyphs
Not Used
Not Used
Figurines
Not Yet Used
Used
Formation
The banded iron layers are formed in sea water when oxygen is released by photosynthetic cyano-bacteria. The oxygen then combines with dissolved iron in ocean to form insoluble iron oxides, which precipitated out, forming a thin layer of banded iron formation on ocean floor.
Porphyry is formed in two stages: the magma cools slowly deep within the crust or the magma is cools rapidly as it erupts from a volcano, creating small grains that are usually invisible to naked eye.
Mineral Content
Hematite, Magnetite, Quartz
Biotite, Chert, Feldspar, Garnet, Graphite, Quartz, Silica
Compound Content
Fe, Iron(III) Oxide, Silicon Dioxide
Aluminium Oxide, CaO, Iron(III) Oxide, Potassium Oxide, MgO, Sodium Oxide, Silicon Dioxide, Titanium Dioxide
Types of Metamorphism
Not Applicable
Burial Metamorphism, Cataclastic Metamorphism, Contact Metamorphism, Hydrothermal Metamorphism, Impact Metamorphism, Regional Metamorphism
Types of Weathering
Chemical Weathering
Biological Weathering, Chemical Weathering, Not Registered
Types of Erosion
Coastal Erosion, Wind Erosion
Chemical Erosion, Coastal Erosion, Glacier Erosion
Grain Size
Large and Coarse Grained
Fine Grained
Fracture
Uneven, Splintery or Conchoidal
Irregular
Porosity
Highly Porous
Less Porous
Cleavage
Imperfect
Imperfect
Specific Gravity
5.0-5.3
2.5-4
Transparency
Translucent to Opaque
Translucent to Opaque
Density
Not Available
2.5-2.52 g/cm3
Specific Heat Capacity
Not Available
Resistance
Heat Resistant, Impact Resistant, Pressure Resistant, Wear Resistant
Heat Resistant, Impact Resistant
Deposits in Eastern Continents
Asia
China, India, Iran, Iraq, Oman, Russia, Saudi Arabia, Taiwan, Thailand, Vietnam
China, Kazakhstan, South Korea, Thailand, Turkey, Vietnam
Africa
Kenya, Morocco, South Africa, Tanzania
Egypt, Ethiopia, Ghana, South Africa
Europe
Austria, France, Greece, Italy, Malta, Poland, Portugal, Serbia, Spain, Sweden, United Kingdom
Finland, France, Germany, Great Britain, Hungary, Iceland, Ireland, Italy, Netherlands, Norway, Romania, Sweden, Switzerland
Others
Greenland, Mid-Atlantic Ridge
Greenland
Deposits in Western Continents
North America
Canada, Mexico, USA
Canada, Cuba, Jamaica, USA
South America
Bolivia, Brazil
Bolivia, Brazil, Colombia, Ecuador, Paraguay
Deposits in Oceania Continent
Australia
New South Wales, Queensland, South Australia, Western Australia
New South Wales, New Zealand, Western Australia