gemstone

Hawk's Eye (Blue Tiger's Eye)

Silicified crocidolite (pseudomorph of Quartz, SiO2, after Riebeckite)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on the Mohs scale; Color: dark blue-gray, bluish-black, with golden-yellow or brown patches (transitioning to Tiger's Eye); Luster: silky to vitreous when polished; Crystal structure: trigonal (microcrystalline quartz); Cleavage: none; Specific gravity: 2.64-2.71;…

Hardness: 6
Luster: silky to vitreous when polished

Identified October 3, 2026More gemstone →

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Physical properties

Formation & geological history

Formed through a metamorphic/hydrothermal process known as pseudomorphism, where parallel, fibrous blue asbestos minerals (crocidolite) are progressively replaced by microcrystalline silica (quartz) while preserving the fibrous structure.

Uses & applications

Popularly carved into cabochons, polished eggs, beads, spheres, and ornamental jewelry; widely sought after by crystal collectors and lapidary artists.

Geological facts

Hawk's Eye is the unoxidized or partially oxidized precursor to standard golden-brown Tiger's Eye. If the iron within the crocidolite oxidizes fully, it turns into golden-yellow goethite/limonite, forming classic Tiger's Eye. This specimen shows a transition zone with golden patches near the top.

Field identification & locations

Identified by its distinctive silky luster, dark bluish-gray tone, and sharp moving band of light (chatoyancy) under direct illumination. Major deposits are found in the Northern Cape Province of South Africa, Western Australia, and parts of Brazil and India.