sedimentary
Banded Iron Formation (BIF) / Jasper
Magnetite / Hematite-bearing Chert / Jasper
Hardness: 6.5-7 (Mohs scale); Color: Red, brown, black, orange; Luster: Vitreous to dull; Crystal structure: Microcrystalline (Cryptocrystalline); Cleavage: None; Specific Gravity: 2.6 - 3.4 depending on iron content.
- Hardness
- 6
- Color
- Red, brown, black, orange
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6.5-7 (Mohs scale); Color: Red, brown, black, orange; Luster: Vitreous to dull; Crystal structure: Microcrystalline (Cryptocrystalline); Cleavage: None; Specific Gravity: 2.6 - 3.4 depending on iron content.
Formation & geological history
Formed in ancient ocean environments during the Precambrian era (approx. 1.8 to 2.5 billion years ago) through the precipitation of iron and silica due to the rise of oxygen from early photosynthetic life.
Uses & applications
Primarily mined as a global source of iron ore; also used for lapidary work, jewelry, and as decorative river stones.
Geological facts
These rocks represent a significant 'snapshot' of Earth's early atmosphere transition. The red bands are typically jasper/chert, while the darker bands contain iron oxides like hematite or magnetite.
Field identification & locations
Identify by the distinct colorful banding and high density. Commonly found in ancient shield areas like Lake Superior (USA/Canada), Western Australia, and Brazil. Magnetite-rich specimens will attract a magnet.
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