Orpiment | Gemopedia

Orpiment is an arsenic sulfide that grows in small masses with lemon-yellow to brownish-yellow coloring. Its name comes from a Latin term meaning "gold pigment," as this mineral was once used to make yellow paint. This gem is photosensitive and should not be exposed to light for prolonged periods.
Alternate
Names
Yellow Arsenic
Colors
Orange-Yellow, Golden Yellow, Brownish Yellow To Lemon Yellow

Orpiment Classification

Common Name

Orpiment

Species

Orpiment

Variety

Colors

Orange-Yellow, Golden Yellow, Brownish Yellow To Lemon Yellow

Alternate Names

Yellow Arsenic

Gemstone Groups

Key Separations

OTL RI, SG and extreme fire.

Comments

This stone contains arsenic and special care needs to be used. Always wash your hands after handling.

Orpiment Optical Properties

Transparency

Transparent - Translucent

Refractive Index

Over the Limit 2.4-3.02

Birefringence

0.62

Optic Character

Biaxial

Optic Sign

Negative

Polariscope Reaction

Doubly Refractive (DR)

Fluorescence

SWUV: Inert
LWUV: Inert

CCF Reaction

Pleochroism

Dichroic, strong yellow and greenish yellow

Dispersion

Strength: extreme fire

Comments

Orpiment Chemistry & Crystallography

Chemical Name

arsenic sulfide

Chemical Formula

As2S3

Synthesis

Crystal System

Monoclinic

Classification

Sulfide

Nature

Natural

Crystallinity

Crystalline to Aggregate

Comments

Orpiment Characteristic Physical Properties

Hardness

1.5-2

Streak

Light Lemon Yellow

Specific Gravity

3.4-3.56 Typical:3.49

Toughness

Poor

Inclusions

Orpiment is usually found as a fibrous aggregate.

Luster

Pearly

Stability

Fracture

Cleavage

Perfect, in one direction, Good, in one direction

Comments

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