Watermelon Tourmaline | Gemopedia

Watermelon tourmaline is an interesting multi-colored elbaite variety. Gems are usually fashioned in thin polished slices to display the crystal's concentric color rings. If you use your imagination, the green represents the skin of the watermelon, white makes up the rind, and pink is the sweet fruit. Incredibly, the colors of watermelon tourmaline are 100% natural, a rare occurrence in nature that makes the gem highly collectable.
Colors
Pink Center With Green Edges

Watermelon Tourmaline Classification

Common Name

Watermelon Tourmaline

Species

Tourmaline

Variety

Watermelon Tourmaline

Colors

Pink Center With Green Edges

Alternate Names

Gemstone Groups

Key Separations

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

Comments

Not all watermelon 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.

Watermelon 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, medium to strong, varying shades of body color

Dispersion

Strength: moderate fire Value: 0.017

Comments

Watermelon 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

Watermelon Tourmaline Characteristic Physical Properties

Hardness

7-7.5

Streak

White

Specific Gravity

3-3.26 Typical:3.06

Toughness

Good

Inclusions

Watermelon tourmaline is Type II clarity stone. Color zoning with pink core and green edges. 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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