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Achroite

Tourmaline

By Tim Matthews, JD, FGA, GG, DGA,
CEO and President of JTV
Published: June 2014
Modified: February 2022
Achroite Polished
Table of Contents
  • General Information
  • Achroite Colors
  • Countries of Origin
  • History
  • Care

Achroite refers to the colorless variety of tourmaline. It gets its name from the Greek word "άχρωμος" or achroos which means without color. The material is almost always the elbaite variety tourmaline, but not always. Many specimens are included, or fibrous, clean gemstones are very rare and especially prized by collectors. Most Achroite is untreated, but some pale colored tourmaline might be heated to remove color. Most stones contain Manganese and Magnesium. The material from the Island of Elba, Italy will fluoresce. Some of the best examples come from Afghanistan, Namibia, Pakistan, and the United States.

General Information

  • Classification
  • Optical Properties
  • Characteristic Physical Properties
  • Chemistry & Crystallography
Common Name
Achroite
Species
Tourmaline
Transparency
Transparent - Opaque
Dispersion
Strength: Weak Fire Value: 0.017
Refractive Index
1.617-1.644 Tolerance: (+0.011/-0.009)
Birefringence
0.018- 0.020
Optic Character
Uniaxial
Optic Sign
Negative
Polariscope Reaction
Doubly Refractive (DR)
Fluorescence
SWUV: Yellow: material from the Island of Elba, Italy; Strong violet: Specimens Nuristan Province Afghanistan
LWUV: Blue: material from the Island of Elba, Italy
Pleochroism
None
Hardness
7-7.5
Streak
White
Specific Gravity
3.000-3.260 Typical:3.060
Toughness
Fair
Inclusions
Achroite has liquid and gas inclusions that are long and thin, reflective gas-filled fractures and color zoning. Lepedilite in Afghanistan material.
Luster
Vitreous
Stability
Very Good
Fracture
Conchoidal, Uneven
Cleavage
Poor
Chemical Name
complex boro-silicate of Al, Mg and Fe
Chemical Formula
Na(Li1.5Al1.5)Al6(Si6O16)(BO3)3(OH)3(OH)
Crystal System
Trigonal
Chemistry Classification
Silicate

Achroite Colors

  • Colorless Achroite
    Colorless

Countries of Origin

Tanzania, United Republic Of; Afghanistan; Czechia; Sri Lanka; United States of America; Madagascar; United Kingdom of Great Britain and Northern Ireland; Bolivia (Plurinational State of); India; Spain; Unknown; Namibia; Italy; Australia; Nepal

History

Achroite was originally discovered on the island of Elba, Italy in 1913.

Care

Normal Care

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