Liddicoattite | Gemopedia

Liddicoattite is a calcium-rich lithium species of tourmaline. Named in 1977 in honor of noted gemologist Richard T. Liddicoat. This gem is distinguished from other parti-colored tourmalines by exhibiting many colors in strongly zoned, geometric color patterns. Tourmaline is derived from the Sinhalese word turamali meaning mixed or stone of mixed colors, likely because of the variety of colors it's found in. Tourmaline is the name for an entire group of gemstones, but some color varieties, such as liddicoattite, have their own names.
Alternate
Names
Fluor-Liddicoattite

Liddicoattite Classification

Common Name

Liddicoattite

Species

Tourmaline

Variety

Liddicoattite

Colors

green, red, pink, purple, blue, colorless, black, brown, yellow and orange frequently multi-colored

Alternate Names

fluor-liddicoattite

Gemstone Groups

Key Separations

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

Comments

Name after Richard T. Liddicoat pioneering gemologist at GIA

Liddicoattite Optical Properties

Transparency

Transparent To Translucent

Refractive Index

1.624 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

Value: usually medium to strong, sometimes two different shades of body color, sometimes two quite different colors

Dispersion

Strength: weak fire Value: 0.017

Liddicoattite Chemistry & Crystallography

Chemical Name

calcium lithium aluminum bora-silicate hydroxide

Chemical Formula

Ca(Li2Al)Al6(Si6O18)(BO3)3(OH)3(OH)

Synthesis

Crystal System

Trigonal

Classification

Silicate

Nature

Natural

Crystallinity

Crystalline

Liddicoattite Characteristic Physical Properties

Hardness

7.5

Streak

light brown, white

Specific Gravity

Typical: 3.02

Toughness

Good

Inclusions

Liddicoattite 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 To Uneven

Cleavage

Difficult, Indistinct

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