sedimentary
Banded Iron Formation (Jaspillite)
Banded Iron Formation (BIF) / Jaspillite
Hardness: 6.5-7 (Mohs scale); Color: Alternating red (jasper) and silver-gray to black (hematite/magnetite) bands; Luster: Sub-metallic to vitreous; Crystal Structure: Trigonal; Fracture: Conchoidal; Specific Gravity: 3.2-5.3
- Hardness
- 6
- Luster
- Sub-metallic to vitreous
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Alternating red (jasper) and silver-gray to black (hematite/magnetite) bands; Luster: Sub-metallic to vitreous; Crystal Structure: Trigonal; Fracture: Conchoidal; Specific Gravity: 3.2-5.3
Formation & geological history
Formed in ancient marine environments during the Precambrian era (approx. 2.4 - 1.8 billion years ago) through the precipitation of iron and silica due to increasing oxygen levels from early photosynthesis.
Uses & applications
Primary source of iron ore globally for steel production; also used as a decorative gemstone and lapidary material for jewelry and cabochons.
Geological facts
These rocks provide a geological record of the 'Great Oxygenation Event.' Some of the oldest known BIFs are over 3.7 billion years old. Famous deposits include the Hamersley Range in Australia and the Mesabi Range in the USA.
Field identification & locations
Identify by distinct red and black striping/banding; check for magnetism if magnetite is present. Commonly found in shield areas of continents like India, Australia, Brazil, and the Lake Superior region of North America.
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