sedimentary
Ironstone (likely Ferruginous Siltstone/Sandstone)
Ferruginous sedimentary rock (FeOx-rich clastic)
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 More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
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).
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.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary