Thulite
Thulite is a manganese-bearing pink variety of zoisite used primarily in ornamental work and cabochons; it is opaque to translucent with a characteristic rose-pink color from Mn substitution in the zoisite structure.
Physical & Optical Properties
RI Range1.691–1.704
SG Range3.10–3.38
SG Typical3.20
Hardness (Mohs)6–7
Crystal SystemOrthorhombic
Optic CharacterDR Biaxial (+)
Birefringence0.009
Dispersion0.012
Fluorescence LWInert
Fluorescence SWInert
Chelsea FilterInert
PleochroismWeak
ColorsRed Pink
SpeciesZoisite
VarietyThulite (Manganese-Bearing Pink Zoisite)
Related: Zoisite Varieties
Key Differentiators
- Opaque to translucent pink zoisite — massive habit, typically cabochon or ornamental
- Higher RI (1.691–1.704) and SG (~3.20) than rose quartz (RI 1.544, SG 2.65) — easy separation by refractometer
- Softer than rhodonite (H 5.5–6.5) with lower RI (rhodonite RI 1.716–1.752, SG 3.57–3.76)
- No black MnO veining (unlike rhodonite which shows diagnostic black vein network)
- Named for Thule (ancient name for Norway) — type locality Leksvik, Norway; also Tanzania and North Carolina
Common Simulants
- Rhodonite: Rhodonite: RI 1.716–1.752, SG 3.57–3.76 (higher than thulite); black MnO dendritic veining; triclinic crystal system.
- Rose Quartz: Rose quartz: RI 1.544–1.553, SG 2.65 — much lower RI and SG than thulite; trigonal, uniaxial DR; translucent milky pink without zoisite texture.
- Rhodochrosite: Rhodochrosite: much softer (H 3.5–4), RI 1.600–1.816 (extreme birefringence), effervesces with dilute HCl; shows concentric white-pink banding.
- Pink Aragonite / Pink Calcite: Carbonate mineral: H ~3, effervesces with HCl; RI 1.530–1.685 range depending on variety; much lower hardness and SG.
Treatments
- Wax / Resin Impregnation (ornamental surface treatment)
Price Context
Natural — low ($/ct)$5
Natural — high ($/ct)$30
NotePer carat equivalent; primarily ornamental value; carved pieces and fine cabochons command modest premiums; most material is tumbled or decorative
Price context is approximate. GemID is not an appraisal tool. Results are indicators, not certified valuations.
About Thulite
Thulite is a manganese-bearing pink variety of zoisite used primarily in ornamental work and cabochons; it is opaque to translucent with a characteristic rose-pink color from Mn substitution in the zoisite structure.
Identifying a thulite? GemID walks through these tests in order — RI, SG, fluorescence, and more.
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