Definition
Banded iron formation are distinctive units of sedimentary rock that are almost always of Precambrian age
Variolites are a group of dark green basic igneous rocks which exhibit pale colored spots, or spherules, especially on weathered surfaces, that give them a pockmarked appearance
Origin
Western Australia, Minnesota
France
Discoverer
Unknown
Unknown
Etymology
From its formation process
From Latin varius, speckled, variegated
Class
Sedimentary Rocks
Igneous Rocks
Sub-Class
Durable Rock, Medium Hardness Rock
Durable Rock, Hard Rock
Group
Not Applicable
Volcanic
Other Categories
Coarse Grained Rock, Opaque Rock
Opaque Rock
Texture
Banded, Trellis
Glassy, Massive, Porphyritic, Scoriaceous, Vesicular
Color
Red, Reddish Brown
Black, Brown, Light to Dark Grey
Durability
Durable
Durable
Scratch Resistant
Yes
Yes
Appearance
Layered, Banded, Veined and Shiny
Dull and Soft
Interior Uses
Decorative Aggregates, Homes
Floor Tiles, Flooring, Homes, Hotels, Kitchens
Exterior Uses
Paving Stone, Office Buildings
Garden Decoration, Office Buildings
Other Architectural Uses
Curbing, Whetstones
Curbing
Construction Industry
As Dimension Stone, Used for flooring, stair treads, borders and window sills.
As Dimension Stone, Cobblestones, Rail Track Ballast, Roadstone
Medical Industry
Not Yet Used
Not Yet Used
Antiquity Uses
Artifacts
Artifacts, Monuments, Sculpture
Commercial Uses
As a touchstone, Cemetery Markers, Creating Artwork
Cemetery Markers, Creating Artwork
Types
Algoma-type , Lake Superior-type, Superior-type and Taconite
Not Available
Features
Is one of the oldest rock
Has High structural resistance against erosion and climate, Very fine grained rock
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
Used
Petroglyphs
Not Used
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.
Variolites are a group of dark green basic igneous rocks that exhibit pale colored spots on weathered surfaces that give them a pockmarked appearance.
Mineral Content
Hematite, Magnetite, Quartz
Olivine, Plagioclase, Pyroxene
Compound Content
Fe, Iron(III) Oxide, Silicon Dioxide
Aluminium Oxide, CaO, Iron(III) Oxide, FeO, Potassium Oxide, MgO, MnO, Sodium Oxide, Phosphorus Pentoxide, 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, Mechanical Weathering
Types of Erosion
Coastal Erosion, Wind Erosion
Not Applicable
Grain Size
Large and Coarse Grained
Not Applicable
Fracture
Uneven, Splintery or Conchoidal
Conchoidal
Streak
White
White to Grey
Porosity
Highly Porous
Less Porous
Luster
Earthy
Not Available
Compressive Strength
Not Available
Cleavage
Imperfect
Not Available
Specific Gravity
5.0-5.3
2.8-3
Transparency
Translucent to Opaque
Opaque
Density
Not Available
2.9-3.1 g/cm3
Resistance
Heat Resistant, Impact Resistant, Pressure Resistant, Wear Resistant
Heat Resistant, Pressure Resistant, Wear Resistant
Deposits in Eastern Continents
Asia
China, India, Iran, Iraq, Oman, Russia, Saudi Arabia, Taiwan, Thailand, Vietnam
India, Russia
Africa
Kenya, Morocco, South Africa, Tanzania
South Africa
Europe
Austria, France, Greece, Italy, Malta, Poland, Portugal, Serbia, Spain, Sweden, United Kingdom
Iceland
Others
Greenland, Mid-Atlantic Ridge
Not Yet Found
Deposits in Western Continents
North America
Canada, Mexico, USA
Canada, USA
South America
Bolivia, Brazil
Brazil
Deposits in Oceania Continent
Australia
New South Wales, Queensland, South Australia, Western Australia
Not Yet Found