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Iron Oxide Concretion
Iron oxide concretions are a type of sedimentary rock formation that are created by the interaction of iron minerals and groundwater in porous rocks. They can be found on Earth and Mars.
Colors It Comes In -
Dark brown to orange: Found in the Tibooburra-Milparinka region of New South Wales
Red: The color of hematite, an iron oxide that is named after the Greek word for blood
Yellow ochre: A dull yellow color that is a hydrate of iron oxide red
Warm red: A color that is a hydrate of iron oxide red
Fracture Pattern - Cube like
Shape -
Spherical: Iron oxide concretions can be spherical or flattened spheres.
Multi-sided: Iron oxide concretions can be 3 to 6 sided bodies that form in a single flat bed.
Ellipsoidal: Iron oxide concretions can be ellipsoidal in shape.
Elongated: Iron oxide concretions can be elongated in shape.
Cylindrical: Iron oxide concretions can be cylindrical in shape.
Irregular: Iron oxide concretions can be irregular in shape.
Ovoid: Iron oxide concretions can be ovoid in shape.
Spindle: Iron oxide concretions can be spindle in shape.
Platter-shaped: Iron oxide concretions can be platter-shaped masses.
Indented: Iron oxide concretions can be indented, with deeply infolded rinds.
Luster - Shiny to dull
Texture - botryoidal
Where It Can Be Found -
Navajo Sandstone, Utah:
These dark spheres are found in the red and white outcrops of Navajo Sandstone in the Southwestern United States. The concretions are made of a sandstone core surrounded by a hard iron-rich rind.
Djadokhta Formation, Mongolia:
These concretions are found in the Cretaceous Djadokhta Formation in the Gobi Desert.
Tibooburra and Milparinka:
These areas have small to large areas of ground littered with dark brown iron oxide fragments.
Fort Massac State Park:
Iron oxide concretions can be found at Fort Massac State Park.
Hardness On The Mohs Scale - These Numbers Below Are Ranked On A 1 To 10 Scale
Hematite
Has a hardness of 5.5–6.5 on the Mohs scale. Hematite concretions can be identified by their red streak, metallic appearance when cut, and specific gravity of 4–5.
Magnetite
Has a hardness of 5–6 on the Mohs scale. Magnetite is a black or brownish-black mineral with a metallic luster.
Micaceous iron oxide
Has a hardness of 6 on the Mohs scale. Micaceous iron oxide is used to increase the wear resistance of coatings.
Goethite
Has a hardness of 5.0–5.5 on the Mohs scale. Goethite is the main component of rust and bog iron ore.
