mineral
Hematite-rich ironstone concretion
Hematite (Fe₂O₃), likely mixed with goethite/limonite and silica
AI-generated identification · may be incorrectDark reddish-brown, earthy to submetallic luster, massive and porous with an irregular cavity; hematite hardness 5–6.5 Mohs, specific gravity about 5.0–5.3, with no visible cleavage. A red-brown streak on unglazed ceramic is diagnostic.
Identified More mineral →
Explore Hematite-rich ironstone concretion in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Dark reddish-brown, earthy to submetallic luster, massive and porous with an irregular cavity; hematite hardness 5–6.5 Mohs, specific gravity about 5.0–5.3, with no visible cleavage. A red-brown streak on unglazed ceramic is diagnostic.
Formation & geological history
Likely formed as a weathering or sedimentary iron-oxide concretion, where iron minerals precipitated and cemented surrounding sediment; age cannot be determined from the photograph. The cavity may reflect dissolution, gas space, or removal of softer material.
Uses & applications
Iron oxides are mined as iron ore and used as pigments; attractive specimens are collected, though this irregular piece has little industrial or jewelry value.
Geological facts
Hematite commonly produces a distinctive red streak even when its surface appears black or brown. Goethite-rich varieties may develop yellow-brown earthy coatings.
Field identification & locations
Common in weathered iron-rich soils, banded iron formations, stream gravels, and sedimentary deposits worldwide. Test streak and magnetism: hematite is usually nonmagnetic or weakly magnetic, while associated magnetite is strongly magnetic.
