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Tourmaline · Variety of Tourmaline

Indicolite

Blue to blue-green tourmaline

Blue
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

Pakistan Pakistan: Shigar / Swat / Sapat Valley
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Important source for aquamarine, topaz, peridot, tourmaline and rare minerals.

31.2% est. supply
Afghanistan Afghanistan: Panjshir / Nuristan / Badakhshan
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Known for emerald, tourmaline, kunzite, lapis lazuli and rare minerals.

26.5% est. supply
Brazil Brazil: Minas Gerais / Paraíba / Bahia
Major

Major source for beryl, tourmaline, quartz, topaz, chrysoberyl and rare minerals.

21.2% est. supply
Nigeria Nigeria: Oyo / Ogun / Plateau fields
Major

Important source for tourmaline, sapphire, garnet, beryl and topaz.

21.2% 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 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