Tourmaline · Variety of Tourmaline
Mint Tourmaline
Pastel mint to soft sage green; sometimes with a blue component
Mint Green
Pale Green
Optical characteristics
- Ref. index
- 1.62 – 1.64
- Birefringence
- 0.018 – 0.04
- Luster
- Vitreous
- Pleochroism
- Moderate Moderate dichroism: pale mint green to near-colorless.
- Fluorescence
- Inert.
Source localities
Tanzania
Tanzania: Merelani Hills
Major
★ Top Source
Sole source of tanzanite worldwide; also produces tsavorite, ruby, sapphire and rare collector gems including fine mint tourmaline.
Kenya
Kenya: Tsavo region
Significant
Classic source for tsavorite and other East African garnets.
Mozambique
Mozambique: Montepuez / Alto Ligonha / Cuamba
Significant
Major modern source for ruby, garnet, tourmaline and Paraíba-type tourmaline.
Nigeria
Nigeria: Oyo / Ogun / Plateau fields
Significant
Important source for tourmaline, sapphire, garnet, beryl and topaz.
Enhancement & treatment
Inclusions & features
Needles Growth Tubes, Rain Inclusions
Under 10x loupe: long thin hollow channels running parallel to each other and to…
Zoning Color Zoning
Under 10x loupe in immersion: bands or patches of deeper or lighter color arranged…
Crystals Crystal Inclusions
Under 10x loupe: solid, well-formed mineral crystals trapped inside the host gem. They may…
Multiphase Two-Phase Inclusions
Under 10x loupe: a transparent irregular cavity containing both a liquid phase and a…
Instruments used
Refractometer
Measures refractive index, the backbone of gem identification
Dichroscope
Reveals pleochroism, instantly eliminates singly-refractive stones
10x Loupe
Your most-used instrument, start every examination here
Polariscope
Determines single vs. double refraction, quick and conclusive
Trace Element Analyzer
Chemical testing for diffusion, origin clues, and trace-element treatment detection