Bastnaesite | Gemopedia

A rare gem, bastnaesite is named after the Swedish locality where it was originally discovered in 1841, the Bastnas mines. Color can range from honey yellow to reddish brown and crystals vary from transparent to translucent in appearance. Valued by industry as a source of rare-earth elements, bastnaesite is rare, but has been found in small quantities throughout the world. It is difficult to cut because it is a relatively soft mineral, however, its high refractive index, combined with its rarity, make it an exciting gem to own.
Alternate
Names
BastnSite
Colors
Orange Brown, Brown, Yellow, Orangish Yellow

Bastnaesite Classification

Common Name

Bastnaesite

Species

Bastnaesite

Variety

Colors

Orange Brown, Brown, Yellow, Orangish Yellow

Alternate Names

BastnSite

Gemstone Groups

Key Separations

RI and birefringence

Comments

Strongly piezoelectric: development of opposite charges at the ends of the crystal when placed under stress.

Bastnaesite Optical Properties

Transparency

Transparent

Refractive Index

Over the Limit 1.717-1.823

Birefringence

0.1

Optic Character

Uniaxial

Optic Sign

Positive

Polariscope Reaction

Doubly Refractive (DR)

Fluorescence

SWUV:
LWUV:

CCF Reaction

Pleochroism

Unobservable

Dispersion

Strength: none

Comments

Bastnaesite Chemistry & Crystallography

Chemical Name

cerium carbonate fluoride

Chemical Formula

(Ce,La)(CO3)F

Synthesis

Crystal System

Hexagonal

Classification

Carbonate

Nature

Natural

Crystallinity

Crystalline

Comments

Bastnaesite Characteristic Physical Properties

Hardness

4-4.5

Streak

Specific Gravity

4.78-5.2

Toughness

Poor

Inclusions

Luster

Vitreous

Stability

Poor

Fracture

Uneven

Cleavage

Poor, in one direction

Comments

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