Paraiba Tourmaline | Gemopedia

When Paraba tourmaline was first discovered in Brazil in the 1980's, the unusually intense "neon" or "electric" blues and greens set it apart from any other tourmaline previously known. The color of this gem ranges from intense emerald green through vivid Caribbean blue to a rich sapphire blue. Apart from its intense colors, another key feature of Paraba tourmaline is its relative lack of extinction, best described as a lifeless area within a stone.
Colors
Bright Electric Blue To Green, Violet To Purplish

Paraiba Tourmaline Classification

Common Name

Paraiba Tourmaline

Species

Elbaite

Variety

Paraiba Tourmaline

Colors

Bright Electric Blue To Green, Violet To Purplish

Alternate Names

Gemstone Groups

Tourmaline

Key Separations

appearance, refractive index and high birefringence; then optic figure, pleochroism and specific gravity. Has intense saturated color.

Comments

Crystal habit is prismatic and may be 3, 6 or 9-sided; often a triangular prism with convex faces, and often long and heavily striated parallel to the c axis. Pyramidal terminations are common. Tourmaline is part of an isomorphous series.Cuprian Elbaite must have copper present to be called Paraiba tourmaline.Originally found in the Brazilian State of ParaibaDark material might have a birefringence as high as 0.040.

Paraiba Tourmaline Optical Properties

Transparency

Transparent

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

Paraiba 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) with Cu

Synthesis

Crystal System

Trigonal

Classification

Silicate

Nature

Natural

Crystallinity

Crystalline

Comments

Paraiba Tourmaline Characteristic Physical Properties

Hardness

7-7.5

Streak

White

Specific Gravity

3-3.26 Range:0.2/-0.06 Typical:3.06

Toughness

Good

Inclusions

Paraiba tourmaline is a type II clarity stone. 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

Cleavage

Poor, in two directions

Comments

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