Parti-Colored Tourmaline | Gemopedia

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

Parti-Colored Tourmaline Classification

Common Name

Parti-Colored Tourmaline

Species

Tourmaline

Variety

Parti-Colored Tourmaline

Colors

variations of two or more colors usually green, blue and red

Alternate Names

bi-color tourmaline

Gemstone Groups

Key Separations

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

Comments

Not all parti-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.

Parti-Colored Tourmaline Optical Properties

Transparency

Transparent To Translucent

Refractive Index

1.624-1.644 Tolerance: +0.011/-0.009

Birefringence

0.018-0.02

Optic Character

uniaxial

Optic Sign

negative

Polariscope Reaction

doubly refractive (DR)

Fluorescence

SWUV: Variable
LWUV: Variable

CCF Reaction

Pleochroism

Value: Medium to strong variations of bodycolor and dependent on area tested

Dispersion

Strength: moderate fire Value: 0.017

Comments

Parti-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

Parti-Colored Tourmaline Characteristic Physical Properties

Hardness

7-7.5

Streak

white

Specific Gravity

3-3.26

Toughness

Good

Inclusions

Parti-colored tourmaline 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 and Uneven

Cleavage

Difficult, Indistinct

Comments

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