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Hawk's Eye

Last updated: April 2026

Blue-grey to blue-green chatoyant quartz formed where crocidolite asbestos is replaced by silica without iron oxide oxidation (which produces golden Tiger's Eye). The retained blue color of the asbestos gives Hawk's Eye its steely blue-grey to greenish-blue hue. Always cut en cabochon. Often found alongside Tiger's Eye in the same host rock.

Hawk's Eye has a specific gravity of 2.65 and a refractive index of 1.544–1.553, with a Mohs hardness of 7. It is aggregate.

Physical & Optical Properties

RI Range1.544–1.553
SG Range2.64–2.71
SG Typical2.65
Hardness (Mohs)7
Crystal SystemTrigonal
Optic CharacterAggregate
Dispersion0.013
Fluorescence LWInert
Fluorescence SWInert
Chelsea FilterInert
PleochroismNone
ColorsBlue Violet, Green
SpeciesQuartz
Blue VioletGreen

AgateAmethystAmetrineAventurineBloodstoneCarnelianChalcedonyChrysopraseCitrineOnyxPrasioliteRock CrystalRose QuartzSmoky QuartzTiger's Eye

Key Differentiators

Treatments

Price Context

Natural — low ($/ct)$1
Natural — high ($/ct)$15
NotePer carat; less common than Tiger's Eye; value driven by depth and uniformity of blue color and chatoyancy quality

Price context is approximate. Loupewise is not an appraisal tool. Results are indicators, not certified valuations.

Measurement Guides

How to Identify a GemstoneHow to Measure Specific GravityHow to Use a RefractometerUV Fluorescence Testing

Identifying a hawk's eye? Loupewise walks through these tests in order — RI, SG, fluorescence, and more.

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Studying for the GIA, FGA, or FEEG practical? Hawk's Eye is one of the 130 species in Loupewise’s drill and exam pool — practice identifying it from its measured properties under timed exam conditions.

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