Iris Quartz
Quartz var. Iris Quartz · Semi-Precious Gemstone / Collector Mineral
Crystal System
Trigonal; typically occurs in hexagonal prismatic habits with pyramidal terminations
Mineral Group
Silicates (Tectosilicate subgroup)
Chemical Formula
SiO2
Formation Process
Hydrothermal; forms from silica-rich aqueous solutions cooling in crustal fractures at low to moderate temperatures
About This Crystal
Transparent to translucent colorless quartz featuring internal prismatic 'rainbows' caused by light interference at basal fracture planes or twin boundaries
Physical Characteristics
Colorless body color with white streak; vitreous luster; no cleavage; conchoidal fracture; specific gravity 2.65; non-fluorescent
Optical Properties
Uniaxial positive; refractive index 1.544–1.553; double refraction; exhibits thin-film interference (iridescence) along internal fractures
Hardness & Durability
Origin Region
Notably from India, Brazil, and the USA (Arkansas); forms in hydrothermal veins and pegmatites
Hardness & Durability
Mohs hardness 7; high toughness but internal 'rainbow' areas are structural weaknesses (fractures)
Care & Maintenance
Clean with warm soapy water; avoid ultrasonic cleaners or steam as they may expand the internal fractures and lose the iris effect
Rarity & Value
Uncommon; value depends on the intensity and coverage of the spectral colors; more valuable than standard clear quartz
Special Characteristics
Displays iridescence (rainbow effect) caused by light diffraction through microscopic air or liquid-filled cracks (Schiller effect)
Lore & History
Historically used in scrying; traditionally associated with the Crown Chakra and believed to harmonize all colors of the aura