Tanzanite | Gemopedia

Henry Platt, former president of Tiffany & Co., described tanzanite's discovery in 1967 as THE most important gemstone find in 2000 years! This single 5-mile strip of land in Tanzania remains the only commercially viable source of this stone that has become one of the world's most sought-after and admired gems. Tanzanite is a relatively new gemstone in the world of gemology and jewelry, and though its history is brief, it is no less illustrious than many ancient gems. Tanzanite is a single-source gemstone that is a thousand times rarer than diamond, and is only gaining popularity.
Colors
Blue, Violetish Blue To Violet, Bluish Purple

Tanzanite Classification

Common Name

Tanzanite

Species

Zoisite

Variety

Tanzanite

Colors

Blue, Violetish Blue To Violet, Bluish Purple

Alternate Names

Gemstone Groups

Epidote

Key Separations

refractive index, birefringence, optic character and pleochroism

Comments

Crystal habit is typically an orthorhombic prism with a roughly rectangular cross-section and striations parallel to the c axis on some faces. The zoisite species also occurs in pink, yellow, green and brown varieties. Misnomer: Meru sapphire, 24th Wedding anniversary

Tanzanite Optical Properties

Transparency

Transparent - Translucent

Refractive Index

1.691-1.7
Tolerance:(+0.005/-0.005)

Birefringence

0.008-0.013

Optic Character

Biaxial

Optic Sign

Positive

Polariscope Reaction

Doubly Refractive (DR)

Fluorescence

SWUV: Inert
LWUV: Inert

CCF Reaction

Pleochroism

Trichroic, (in unheated gems) strong blue, purplish red and greenish yellow; (in heated gems) strong blue, slightly lighter blue, and purple

Dispersion

Strength: weak fire Value: 0.021

Comments

Tanzanite Chemistry & Crystallography

Chemical Name

calcium aluminum silicate with hydroxyl (OH)

Chemical Formula

Ca2Al3(SiO4)3(OH)

Synthesis

Crystal System

Orthorhombic

Classification

Silicate

Nature

Natural

Crystallinity

Crystalline

Comments

Tanzanite Characteristic Physical Properties

Hardness

6.5

Streak

White

Specific Gravity

3.1-3.45 Range:0.1/-0.25 Typical:3.35

Toughness

Varies

Inclusions

Tanzanite is a type I clarity stone. Stones rarely contain needles, chromite inclusions, growth and etch tubes.

Luster

Vitreous

Stability

Good

Fracture

Conchoidal, Uneven

Cleavage

Perfect, in one direction, Good, in one direction

Comments

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