Iris Agate | Gemopedia

A semitransparent to translucent member of the chalcedony species, iris agate is a phenomenal variety exhibiting an iridescent rainbow-like range of colors throughout the stone. It is highly prized by collectors and designers.
Colors
Colorless

Iris Agate Classification

Common Name

Iris Agate

Species

Quartz

Variety

Chalcedony

Colors

Colorless

Alternate Names

Gemstone Groups

Key Separations

RI, SG, appearance in transmitted light and fracture

Comments

Stones are usually cut in thin slices so iridescence can be seen in transmitted light

Iris Agate Optical Properties

Transparency

Semitransparent To Translucent

Refractive Index

1.535-1.539

Birefringence

0.004-0.004

Optic Character

Uniaxial

Optic Sign

Positive

Polariscope Reaction

Aggregate (AGG)

Fluorescence

SWUV: Inert
LWUV: Inert

CCF Reaction

Pleochroism

None

Dispersion

Strength: none

Comments

Iris Agate Chemistry & Crystallography

Chemical Name

silicon dioxide (aka silica)

Chemical Formula

SiO2

Synthesis

Crystal System

Trigonal

Classification

Silicate

Nature

Natural

Crystallinity

Polycrystalline

Comments

Iris Agate Characteristic Physical Properties

Hardness

6.5-7

Streak

Specific Gravity

2.55-2.7 Typical: 2.6

Toughness

Excellent

Inclusions

Iris agate iridescence has a banded appearance.

Luster

Vitreous

Stability

Good

Fracture

Conchoidal

Cleavage

None

Comments

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