sedimentary
Ironstone (with possible Hematite/Limonite coating)
Ironstone (Fe-rich sedimentary rock)
Hardness: 5-6 on Mohs scale; Color: Dark brown, reddish-brown to grey; Luster: Sub-metallic to dull/earthy; Crystal structure: Usually massive or fine-grained; Specific gravity: 3.0-5.0 (relatively heavy)
- Hardness
- 5-6 on Mohs scale
- Color
- Dark brown, reddish-brown to grey
- Luster
- Sub-metallic to dull/earthy
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Physical properties
Hardness: 5-6 on Mohs scale; Color: Dark brown, reddish-brown to grey; Luster: Sub-metallic to dull/earthy; Crystal structure: Usually massive or fine-grained; Specific gravity: 3.0-5.0 (relatively heavy)
Formation & geological history
Formed through the chemical precipitation of iron minerals in sedimentary environments or by the weathering and oxidation of iron-rich rocks. Often found in layered beds or as nodules across various geological ages.
Uses & applications
Primarily used as an ore of iron in the steel industry. Occasionally used in construction (road base) or as a landscaping decorative stone.
Geological facts
Ironstones are the primary source for most of the world\'s iron. The vibrant red or yellow colors seen in such rocks are typically due to the oxidation (rusting) of iron minerals present within the matrix.
Field identification & locations
Identify by its notable weight (heaviness), reddish-brown streak on unglazed porcelain, and common occurrence in old river beds or alongside iron-rich strata.
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