Hawk’s Eye

Blue-grey with silky chatoyancy, the unoxidized precursor of tiger's eye

Blue Blue-Grey

Optical properties

Optical characteristics

Ref. index: 1.544 – 1.553
Birefringence: 0.009
Luster: Silky
Pleochroism: None None; chatoyancy is the optical phenomenon, not pleochroism.
Fluorescence: Inert.

Origins

Source localities

South Africa South Africa: Cullinan / Venetia

Significant

Historic and important diamond source; Griqualand West region is world's primary source of hawk's eye.

65% est. supply

India India: Rajasthan / Odisha / Karnataka

Commercial

Historic and modern source for garnet, moonstone, corundum and other gems.

20% est. supply

Namibia Namibia: Erongo / Green Dragon area

Commercial

Known for demantoid, spessartite and collector minerals.

15% est. supply

Inclusions

Inclusions & features

Zoning Color Zoning Under 10x loupe in immersion: bands or patches of deeper or lighter color arranged…

Identification

Instruments used

10x Loupe Your most-used instrument, start every examination here Polariscope Determines single vs. double refraction, quick and conclusive High CRI Penlight Tiny concentrated white spot for field checks, inclusions, fire, and fractures

Specifications

Hardness: 7 Mohs
Ref. index: 1.544 – 1.553
Sp. gravity: 2.64 – 2.71
Birefringence: 0.009
Crystal system: Trigonal
Luster: Silky
Species: Quartz (fibrous crocidolite pseudomorph, unoxidized)

Market price $ 3 – 60 / ct

Rarity Common

Hawks-eye is the unoxidized form of tiger's eye with blue-grey fibrous reflection; fairly common alongside tiger's eye.

Confused with

Tiger's Eye Tiger's eye is the oxidized version — same structure, golden-brown color.
Cat's Eye Chrysoberyl Chrysoberyl is harder, brighter, and a single crystal.

Expert tip

Hawk's eye retains blue-grey crocidolite fibers before iron oxidation converts them to golden tiger's eye; sometimes both colors appear in the same stone.