Hiddenite
Last updated: April 2026
Green chromium-bearing spodumene from North Carolina. True hiddenite (Cr-colored) is very rare; most commercial material sold as 'hiddenite' is iron-colored pale green spodumene or irradiated yellow spodumene. Related gem: kunzite (pink/lilac spodumene).
Hiddenite has a specific gravity of 3.18 and a refractive index of 1.660–1.676, with a Mohs hardness of 6.5–7.0. It is biaxial +.
Physical & Optical Properties
RI Range1.660–1.676
SG Range3.15–3.21
SG Typical3.18
Hardness (Mohs)6.5–7
Crystal SystemMonoclinic
Optic CharacterDR Biaxial (+)
Birefringence0.016
Dispersion0.017
Fluorescence LWInert
Fluorescence SWInert
Chelsea FilterVariable
PleochroismStrong Trichroic
ColorsGreen
SpeciesSpodumene
Related: Spodumene Varieties
Key Differentiators
- Perfect cleavage in two directions — chips easily along cleavage planes
- Biaxial positive (DR_B+) vs emerald (uniaxial negative DR_U-)
- Lower RI than emerald (1.577–1.583); lower SG than emerald (2.67–2.78)
- Strong trichroism (3 colors) vs emerald (dichroic, 2 colors)
- True chromium hiddenite is rare; most commercial 'hiddenite' is iron-colored or irradiated spodumene
Treatments
- Irradiation (unstable green color)
Measurement Guides
Identifying a hiddenite? GemID walks through these tests in order — RI, SG, fluorescence, and more.
Try GemID Free →Studying for the GIA, FGA, or FEEG practical? Hiddenite is one of the 130 species in GemID’s drill and exam pool — practice identifying it from its measured properties under timed exam conditions.
Practice exams →