mineral

Botryoidal Hematite (Kidney Ore)

Hematite (Fe2O3)

Hardness: 5.5-6.5; Color: Steel-gray to black with a submetallic to dull luster; Crystal Structure: Trigonal (often found in botryoidal/mammillary masses); Streak: Characteristic cherry-red to reddish-brown.

Hardness: 5
Color: Steel-gray to black with a submetallic to dull luster
Streak: Characteristic cherry-red to reddish-brown

Identified March 14, 2026More mineral →

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Physical properties

Formation & geological history

Formed as a secondary mineral through the weathering or alteration of iron-rich minerals, or as a primary precipitate from hydrothermal fluids or iron-rich sedimentary environments. Often found in Banded Iron Formations (BIFs).

Uses & applications

Primary ore of iron for steel production. Also used as a pigment (ochre), in jewelry as 'black diamond' substitutes, and as a popular heavy-duty polishing agent known as 'jeweler's rouge'.

Geological facts

The name comes from the Greek word 'haima' meaning blood, due to its red streak. Botryoidal specimens are nicknamed 'Kidney Ore' because of their bumpy, organ-like surface. It is also found in abundance on Mars.

Field identification & locations

Identify in the field by its high density (heavy for its size) and distinct red streak when rubbed on unglazed porcelain. Commonly found in Cumbria (UK), Morocco, Brazil, and the Lake Superior region (USA). Collectors look for the unique bubbly shape and metallic sheen.