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Tourmaline · Variety of Tourmaline

Chrome Tourmaline

Rich chromium/vanadium green tourmaline

Green
Optical properties

Optical characteristics

Ref. index
1.614 – 1.666
Birefringence
0.014 – 0.04
Luster
Vitreous
Pleochroism
Strong Usually strong dichroism; observe along different crystal directions.
Fluorescence
Usually inert to weak.
Origins

Source localities

Tanzania Tanzania: Merelani Hills
Major

Major source for tanzanite, garnet, spinel, tourmaline, ruby and fancy sapphires.

34% est. supply
Kenya Kenya: Tsavo region
Premium ★ Top Source

Classic source for tsavorite and other East African garnets.

51% est. supply
Tanzania Tanzania: Mahenge
Premium ★ Top Source

Chrome tourmaline found alongside the Mahenge spinel deposits.

15% est. supply
Treatments

Enhancement & treatment

Heat Heat Treatment, Tourmaline Heat treatment is used to improve tourmaline color and is often stable. Disclosure is… Color Enhancement Irradiation, Tourmaline Irradiation can alter tourmaline color centers. It may be used alone or followed by…
Inclusions

Inclusions & features

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… Fractures Feathers and Fractures Under 10x loupe: irregular internal surfaces that catch light and appear bright, wing-like, or… Fractures Fingerprint Inclusions Under 10x loupe: curved or wavy lines of tiny dots forming patterns that look… Needles Growth Tubes, Rain Inclusions Under 10x loupe: long thin hollow channels running parallel to each other and to… Crystals Negative Crystals Under 10x loupe: an empty cavity that has the geometric shape of the host… Clouds Pinpoint Clouds Under 10x loupe: concentrations of extremely tiny bright dots that individually are too small… Crystals Radiation Halos Under 10x loupe or microscope: a dark brown, gray, or discolored spherical zone surrounding… Multiphase Two-Phase Inclusions Under 10x loupe: a transparent irregular cavity containing both a liquid phase and a…
Identification

Instruments used

Dichroscope Reveals pleochroism, instantly eliminates singly-refractive stones Immersion Microscope See every internal detail clearly, the professional standard 10x Loupe Your most-used instrument, start every examination here Polariscope Determines single vs. double refraction, quick and conclusive Refractometer Measures refractive index, the backbone of gem identification UV Lamp, Long Wave and Short Wave Fluorescence exposes treatments, synthetics, and origin Chelsea Filter Quick chromium test, key for emeralds and rubies