Multi-Colored Tourmaline | Gemopedia

Multi-colored tourmaline is a variety of tourmaline containing two or more colors displayed in one crystal. Green and pink is the most prevalent combination, but others are possible. Multi-colored tourmaline may be referred to as "bi-colored tourmaline" or "tri-colored tourmaline," etc.
Alternate
Names
Parti-Colored Tourmaline, Bi-Color Tourmaline, Tri-Color Tourmaline
Colors
Variations Of Two, More Colors Usually Green, Blue, Red

Multi-Colored Tourmaline Classification

Common Name

Multi-Colored Tourmaline

Species

Elbaite

Variety

Colors

Variations Of Two, More Colors Usually Green, Blue, Red

Alternate Names

Parti-Colored Tourmaline, Bi-Color Tourmaline, Tri-Color Tourmaline

Gemstone Groups

Tourmaline

Key Separations

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

Comments

Not all multi-colored tourmaline is elbaite tourmaline Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH).Dark material might have a birefringence as high as 0.040.Pyroelectric: development of opposite charges at the ends of a tourmaline crystal due to change in temperature. Piezoelectric: development of opposite charges at the ends of a tourmaline crystal when placed under stress.

Multi-Colored Tourmaline Optical Properties

Transparency

Transparent - Translucent

Refractive Index

1.624-1.644
Tolerance:-1.22222222222222

Birefringence

0.018-0.02

Optic Character

Uniaxial

Optic Sign

Negative

Polariscope Reaction

Doubly Refractive (DR)

Fluorescence

SWUV: Variable
LWUV: Variable

CCF Reaction

Pleochroism

Dichroic, moderate to strong, varying shades of body color

Dispersion

Strength: moderate fire Value: 0.017

Comments

Multi-Colored 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

Multi-Colored Tourmaline Characteristic Physical Properties

Hardness

7-7.5

Streak

White

Specific Gravity

3-3.26 Typical:3.06

Toughness

Good

Inclusions

Multi-colored tourmaline is Type II clarity stone. Stones will have two or more color zones. Stones might contain liquid and gas inclusions that are long and thin, reflective gas-filled fractures and color zoning.

Luster

Vitreous

Stability

Very Good

Fracture

Conchoidal, Subconchoidal, Irregular, Uneven

Cleavage

Poor, in two directions

Comments

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