Achroite | Gemopedia

Achroite refers to the colorless variety of tourmaline. An elbaite tourmaline variety, these gems are very rare and especially prized by collectors.
Colors
Colorless

Achroite Classification

Common Name

Achroite

Species

Tourmaline

Variety

Achroite

Colors

Colorless

Alternate Names

Gemstone Groups

Tourmaline

Key Separations

refractive index and high birefringence; then optic figure and specific gravity

Comments

Achroite Optical Properties

Transparency

Transparent - Opaque

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: Inert
LWUV: Inert

CCF Reaction

Pleochroism

None

Dispersion

Strength: weak fire Value: 0.017

Comments

Achroite 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

Achroite Characteristic Physical Properties

Hardness

7-7.5

Streak

White

Specific Gravity

3-3.26 Typical:3.06

Toughness

Fair

Inclusions

Achroite has 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

Comments

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