metamorphic

Polished tiger iron

Tiger iron; interbanded jasper, hematite/magnetite, and crocidolite pseudomorph (quartz-rich ironstone)

AI-generated identification · may be incorrect

Hardness approximately 6.5–7 overall, with locally softer iron oxides; dark brown to black with ochre-gold mottling, opaque, and glassy to submetallic polish. It is a massive, banded aggregate rather than a single crystal; specific gravity is commonly about 3.0–4.0.

Identified September 11, 2026More metamorphic →

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Physical properties

Formation & geological history

A Precambrian banded iron formation, roughly 2.5–1.8 billion years old, later silicified and enriched in iron oxides; polishing reveals the contrasting jasper and iron-rich bands. Classic material comes from the Pilbara region of Western Australia.

Uses & applications

Commonly cut and polished into cabochons, worry stones, beads, carvings, and decorative objects; it has modest lapidary and collector value rather than major industrial use.

Geological facts

The name reflects its tiger-like brown, gold, and black patterning. Magnetic response may occur where magnetite is abundant, while the polished surface can resemble bronzite or iron-rich jasper.

Field identification & locations

Identify it by opaque reddish-brown/gold-black patterning, very fine grain, high polish, and occasional magnetism; a streak, hardness, and acid test help distinguish it from dyed stones. Similar jasper and ironstone occur worldwide.