Petalite | Gemopedia

Faceted petalite gems and specimens are prized by gemstone and mineral collectors. Petalite's name is derived from the Greek petalos (leaf), referring to its perfect cleavage. Colorless material is common, and large crystals have been mined. Other petalite colors include white to yellow or gray, yellowish green to light green and pink. Crystals range from transparent to translucent and are prized for their good clarity. Faceted gems aren't often seen due to petalite's cleavage planes.
Alternate
Names
Castorite, Pollucite
Colors
Colorless, Gray, Yellow, Pink, Very Light Green

Petalite Classification

Common Name

Petalite

Species

Petalite

Variety

Colors

Colorless, Gray, Yellow, Pink, Very Light Green

Alternate Names

Castorite, Pollucite

Gemstone Groups

Key Separations

RI, birefringence, optic sign and SG

Comments

Petalite Optical Properties

Transparency

Transparent - Translucent

Refractive Index

1.504-1.516
Tolerance:(+0.006/-0.002)

Birefringence

0.12-0.16

Optic Character

Biaxial

Optic Sign

Positive

Polariscope Reaction

Doubly Refractive (DR)

Fluorescence

SWUV: Inert
LWUV: Inert to weak orange

CCF Reaction

Pleochroism

Unobservable

Dispersion

Comments

Petalite Chemistry & Crystallography

Chemical Name

lithium aluminum silicate

Chemical Formula

LiAlSi4O10

Synthesis

Crystal System

Monoclinic

Classification

Silicate

Nature

Natural

Crystallinity

Crystalline to Aggregate

Comments

Petalite Characteristic Physical Properties

Hardness

6-6.5

Streak

White

Specific Gravity

2.39-2.46 Typical:2.4

Toughness

Poor

Inclusions

Luster

Vitreous

Stability

Fracture

Subconchoidal

Cleavage

Perfect, in one direction, Poor, in one direction

Comments

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