Pearl
Last updated: April 2026
An organic gem formed within the soft tissue of a living shelled mollusk.
Pearl has a specific gravity of 2.74 and a refractive index of 1.520–1.690, with a Mohs hardness of 2.5–4.5. It is aggregate.
Physical & Optical Properties
RI Range1.520–1.690
SG Range2.60–2.85
SG Typical2.74
Hardness (Mohs)2.5–4.5
Crystal SystemAggregate
Optic CharacterAggregate
Dispersion0.000
Fluorescence LWVariable
Fluorescence SWInert
Chelsea FilterInert
PleochroismNone
ColorsColorless, Red Pink, Yellow Orange, Black, Brown, Green, Blue Violet
SpeciesOrganic
Related: Organic Varieties
Key Differentiators
- Characteristic orient/luster
- Layered structure (nacre)
- Organic origin
Treatments
- Bleaching (whitening/uniformizing)
- Dyeing (black, pink, etc.)
- Surface Coating / Lacquering
- Irradiation (artificial black color — Tahitian imitation)
Price Context
Natural — low ($/ct)$50
Natural — high ($/ct)$5,000
NotePer strand or per piece (not per carat); natural pearls extremely valuable; Akoya, South Sea, and Tahitian cultured pearls vary widely
Price context is approximate. GemID is not an appraisal tool. Results are indicators, not certified valuations.
Measurement Guides
Identifying a pearl? GemID walks through these tests in order — RI, SG, fluorescence, and more.
Try GemID Free →Studying for the GIA, FGA, or FEEG practical? Pearl 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 →