Sugilite
Last updated: April 2026
A rare cyclosilicate mineral found almost exclusively at the Wessels Mine in the Kalahari Manganese Field, Northern Cape, South Africa. Prized for its vivid purple color — top 'gel' quality is translucent with an intense grape-like purple that commands premium prices.
Physical & Optical Properties
RI Range1.607–1.610
SG Range2.74–2.80
SG Typical2.76
Hardness (Mohs)5.5–6.5
Crystal SystemHexagonal
Optic CharacterDR Uniaxial (−)
Birefringence0.002
Dispersion0.010
Fluorescence LWInert
Fluorescence SWInert
Chelsea FilterInert
PleochroismNone
ColorsPurple
SpeciesSugilite
Key Differentiators
- Vivid purple to violet color, often with rich grape-juice saturation
- Massive polycrystalline habit — no visible crystal faces or transparency
- Primarily from Wessels Mine, Northern Cape, South Africa
- RI 1.607–1.610 distinguishes from amethyst (1.544) and charoite (1.550–1.559)
- SG 2.74–2.80 — heavier than charoite (2.54–2.68) and fluorite (3.18)
Common Simulants
- Charoite: Charoite has distinctive fibrous swirling texture with orange (tinaksite) and black (aegirine) inclusions; RI 1.550–1.559 (lower); SG 2.54–2.68 (lighter).
- Purple Fluorite: Fluorite is transparent, SG 3.18 (much heavier), perfect octahedral cleavage, RI 1.434 (much lower). Easily distinguished.
- Amethyst: Amethyst is crystalline and transparent/translucent, RI 1.544–1.553 (lower), SG 2.65, birefringence 0.009. Sugilite is massive and opaque.
Treatments
- Wax or Resin Impregnation
- Dyed (lower-quality pale material)
Price Context
Natural — low ($/ct)$20
Natural — high ($/ct)$500
NotePer carat; standard opaque $20–80/ct; fine translucent 'gel' quality $100–500+/ct; Wessels Mine material commands premium
Price context is approximate. GemID is not an appraisal tool. Results are indicators, not certified valuations.
Measurement Guides
Identifying a sugilite? GemID walks through these tests in order — RI, SG, fluorescence, and more.
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