mineral

Limonite/goethite-bearing ironstone (probable)

Goethite, α-FeO(OH), commonly mixed with limonite (hydrated iron oxides) and host rock

AI-generated identification · may be incorrect

Rusty brown to black, earthy-to-submetallic luster, irregular massive texture, no obvious cleavage; goethite hardness about 5–5.5 Mohs, specific gravity about 3.3–4.3. The glossy black areas may be manganese oxides or iron-rich glassy surfaces, but cannot be confirmed visually.

Identified August 30, 2026More mineral →

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Physical properties

Formation & geological history

Forms by weathering and oxidation of iron-bearing minerals, commonly as botryoidal coatings, cavity fillings, or gossan material. Age is locality-dependent; this type is common in weathered ore zones and glacial/alluvial deposits around the inland Northwest.

Uses & applications

Used historically as an iron ore and pigment; attractive specimens are collected for their metallic brown-black textures. Usually has little commercial value unless it displays botryoidal forms, crystal sprays, or association with valuable ore minerals.

Geological facts

Limonite is a field term rather than a single precisely defined mineral; much material sold as limonite is chiefly goethite with variable hematite and water content.

Field identification & locations

Likely plausible near Spokane, Washington (47.7°N, 117.4°W), where weathered iron-rich rocks and glacial gravels occur. Confirm with a reddish-brown streak on unglazed ceramic, moderate heft, and lack of fizz in dilute acid; a magnet response may indicate magnetite, though goethite itself is weakly magnetic. Image-only identification is provisional.