Chrome Tourmaline | Gemopedia

First discovered in Tanzania in the 1960's, chrome tourmaline is a fairly new addition to the vast tourmaline family. A true collector's gem, chrome tourmaline exhibits bright green color that resembles, and even rivals, that of the finest emeralds. While it is a type of green tourmaline, not all green tourmalines contain chromium and can be called chrome tourmaline. True chrome tourmaline is more highly prized, as it is a more rare occurrence for chromium to be a coloring agent, which often results in a much brighter and richer green color.
Alternate
Names
Chromtourmaline, Chromium Tourmaline
Colors
Fine Intense Green

Chrome Tourmaline Classification

Common Name

Chrome Tourmaline

Species

Dravite

Variety

Chrome Tourmaline

Colors

Fine Intense Green

Alternate Names

Chromtourmaline, Chromium Tourmaline

Gemstone Groups

Tourmaline

Key Separations

appearance, refractive index and high birefringence; then optic figure, pleochroism and specific gravity

Comments

Stones are colored by chromium or vanadium.Dark stones might have a birefringence as high as 0.040

Chrome Tourmaline Optical Properties

Transparency

Transparent - Opaque

Refractive Index

1.624-1.624
Tolerance:-1.22222222222222

Birefringence

0.018-0.02

Optic Character

Uniaxial

Optic Sign

Negative

Polariscope Reaction

Doubly Refractive (DR)

Fluorescence

SWUV: Inert to weak
LWUV: Inert to weak

CCF Reaction

Reddish

Pleochroism

Dichroic, strong dark green and yellow-green

Dispersion

Strength: moderate fire Value: 0.017

Comments

Chrome Tourmaline Chemistry & Crystallography

Chemical Name

complex boro-silicate of Al, Mg and Fe

Chemical Formula

Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH)

Synthesis

Crystal System

Trigonal

Classification

Silicate

Nature

Natural

Crystallinity

Crystalline

Comments

Chrome Tourmaline Characteristic Physical Properties

Hardness

7-7.5

Streak

White

Specific Gravity

3-3.26 Typical:3.06

Toughness

Good

Inclusions

Chrome tourmaline is a type I clarity stone. Stones might have liquid and gas inclusions that are long and thin, reflective gas-filled fractures and color zoning.

Luster

Vitreous

Stability

Very Good

Fracture

Conchoidal, Uneven

Cleavage

Poor, in two directions

Comments

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