metamorphic
Polished tiger iron
Tiger iron; interlayered hematite, jasper, and crocidolite-quartz (often riebeckite)
AI-generated identification · may be incorrectHardness about 6–7 Mohs; polished surfaces show metallic-to-glassy luster, dark gray/black hematite, red-brown jasper, and golden-brown fibrous bands. It is massive and banded rather than well crystallized, with no obvious cleavage.
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Physical properties
Hardness about 6–7 Mohs; polished surfaces show metallic-to-glassy luster, dark gray/black hematite, red-brown jasper, and golden-brown fibrous bands. It is massive and banded rather than well crystallized, with no obvious cleavage.
Formation & geological history
A banded iron formation metamorphosed and silicified, typically preserving alternating iron-oxide and jasper layers; major deposits are Precambrian, roughly 2.5–1.8 billion years old. Best known from Western Australia.
Uses & applications
Cut and polished for cabochons, beads, carvings, and decorative objects; occasionally used as an ornamental stone. Common polished pieces generally have modest value.
Geological facts
Tiger iron combines the appearance of tiger’s-eye-like fibers with red jasper and dark hematite, producing dramatic natural bands. Its patterns are distinctive but variable.
Field identification & locations
Identify it by three-way banding of black metallic iron oxide, red jasper, and golden-brown fibrous material; a polished finish enhances the contrast. Check that bands are natural and that it is not dyed jasper or manufactured composite.
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