Thulite Gem Guide and Properties Chart

Thulite is the translucent to opaque pink variety of zoisite, which is often mottled or streaked with gray or white quartz. The name thulite is derived from its discovery location, Norway, which was once called Thule. This gem is also called rosaline. Thulite is often cut en cabochon for jewelry manufacture or carved into ornaments.

General Information

Classification
Optical Properties
Characteristic Physical Properties
Chemistry & Crystallography

Common Name

Thulite

Species

Zoisite

Transparency

Translucent - Opaque

Dispersion

Strength: Weak Fire Value: 0.021

Refractive Index

1.691-1.700
Tolerance:(+0.005/-0.005)

Birefringence

0.008-0.013

Optic Character

Biaxial

Optic Sign

Positive

Polariscope Reaction

Aggregate (AGG), Doubly Refractive (DR)

Fluorescence

SWUV: Inert
LWUV: Inert

Pleochroism

Unobservable

Hardness

6-7

Streak

White

Specific Gravity

3.100-3.450 Typical:3.350

Toughness

Varies

Inclusions

Thulite has white veining is due to calcite and the pink color is due to manganese.

Luster

Vitreous, Pearly

Stability

Good

Fracture

Conchoidal, Uneven

Cleavage

Perfect, in one direction, Good, in one direction

Chemical Name

calcium aluminum silicate hydroxide

Chemical Formula

Ca₂Al₃(SiO₄)₃(OH)

Crystal System

Orthorhombic

Chemistry Classification

Silicate

Thulite Colors

Multi-color
Red
Pink

Alternate Names

Rosaline, Unionite

Countries of Origin

Unknown; Norway; United States of America

Care

Normal care