Iris Quartz | Gemopedia

This unique variety of quartz displays phenomenal iridescence. Its beautiful rainbow of color is caused by reflection and refraction of light within the tiny parallel crystal layers within its structure. Fittingly, it is also called "aurora quartz," "iridescent quartz" or "rainbow quartz."
Alternate
Names
    Rainbow Quartz
Colors
Colorless, Slightly Purple, Yellow Displaying Internal Spectral Colors

Iris Quartz Classification

Common Name

Iris Quartz

Species

Quartz

Variety

Iris Quartz

Colors

Colorless, Slightly Purple, Yellow Displaying Internal Spectral Colors

Alternate Names

    Rainbow Quartz

Gemstone Groups

Key Separations

Refractive index, appearance, birefringence, optic character and optic figure. A bull's-eye optic figure is determinative for quartz; may also show Airy's spiral optic figure and Brazil-law twinning under crossed polarizing filters.

Comments

This interference phenomenon in iris quartz is due to reflection and refraction on extremely thin parallel brazil-law twinning lamellae. The rainbow quartz name used for other types of quartz, including those showing internal interference colors caused by fractures ("crack rainbows"), and interference colors caused by superficial thin films of limonite or other minerals.

Iris Quartz Optical Properties

Transparency

Transparent - Translucent

Refractive Index

1.544-1.553
Tolerance:very constant

Birefringence

0.009

Optic Character

Uniaxial

Optic Sign

Positive

Polariscope Reaction

Singly Refractive (SR) With ADR

Fluorescence

SWUV: Inert
LWUV: Inert

CCF Reaction

Pleochroism

None

Dispersion

Strength: weak fire Value: 0.013

Comments

Iris Quartz Chemistry & Crystallography

Chemical Name

silicon dioxide (aka silica)

Chemical Formula

SiO2

Synthesis

Crystal System

Trigonal

Classification

Silicate

Nature

Natural

Crystallinity

Crystalline

Comments

Iris Quartz Characteristic Physical Properties

Hardness

7

Streak

White

Specific Gravity

2.64-2.69 Typical:2.66

Toughness

Good

Inclusions

Iris quartz may contain liquid, two-phase and three-phase inclusions, negative crystals, minerals, needles, rutile and iron particles.

Luster

Vitreous

Stability

Good

Fracture

Conchoidal

Cleavage

None

Comments

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