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Zoisite

Tanzanite

Blue-violet zoisite

Blue Purple
Optical properties

Optical characteristics

Ref. index
1.691 – 1.7
Birefringence
0.009 – 0.013
Luster
Vitreous
Pleochroism
Strong Variable depending on transparency, orientation, and variety.
Fluorescence
Variable to inert.
Origins

Source localities

Tanzania Tanzania: Merelani Hills
Major ★ Top Source

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

100% est. supply
Treatments

Enhancement & treatment

Heat Heat Treatment, Tanzanite Nearly all commercial tanzanite is heated. The treatment is stable and widely accepted.
Inclusions

Inclusions & features

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… Clouds Pinpoint Clouds Under 10x loupe: concentrations of extremely tiny bright dots that individually are too small… Multiphase Two-Phase Inclusions Under 10x loupe: a transparent irregular cavity containing both a liquid phase and a…
Identification

Instruments used

Chelsea Filter Quick chromium test, key for emeralds and rubies 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