sedimentary

Ironstone (likely Ferruginous Siltstone/Sandstone)

Ferruginous sedimentary rock (FeOx-rich clastic)

AI-generated identification · may be incorrect

Hardness: 5-6 (variable based on quartz content); Color: Rusty brown, reddish-orange, dark gray to black; Luster: Dull, earthy to sub-metallic; Crystal Structure: Clastic/Amorphous matrix; Cleavage: None, irregular fracture; Specific Gravity: 3.0-4.5 (heavier than average rock).

Hardness: 5-6 (variable based on quartz content)
Color: Rusty brown, reddish-orange, dark gray to black
Luster: Dull, earthy to sub-metallic

Identified April 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the precipitation of iron oxides (like goethite and hematite) within a sedimentary matrix, often in shallow marine or swampy environments where iron-rich waters react with oxygen. They range in age from Precambrian to recent times.

Uses & applications

Historically used as a low-grade iron ore. In modern times, it is used for gravel, landscaping, and occasionally as a decorative building stone. In the past, it was essential for the early iron industry during the Industrial Revolution.

Geological facts

Ironstone concretions can sometimes contain fossils in their centers. Some types, called 'Bog Iron', were the primary source of iron for Vikings and early American settlers.

Field identification & locations

Identify by its notable weight (high density), rusty appearance, and streak test (usually leaves a reddish-brown or yellow-brown streak on porcelain). It is commonly found in coal-bearing regions and near weathered iron deposits.