Iolite (The main violet gemstone)
Cordierite (Magnesium iron aluminum cyclosilicate) · Semi-Precious Gemstone; Collector Mineral.
Crystal System
Orthorhombic; typically occurs in massive or granular form; short prismatic crystals when well-formed.
Mineral Group
Silicates; Cyclosilicate subgroup.
Chemical Formula
(Mg,Fe)2Al3(AlSi5O18)
Formation Process
Metamorphic; typically forms during regional metamorphism of aluminous rocks or as a primary mineral in granites and pegmatites.
About This Crystal
The center gemstone is a deep violet-blue to greyish-purple cabochon. It exhibits a vitreous luster and is generally translucent to transparent with potential mineral inclusions appearing as dark spots.
Physical Characteristics
Color: Violet-blue; Streak: White; Cleavage: Fair/Poor in one direction; Fracture: Subconchoidal to uneven; Specific Gravity: 2.58–2.66; Weak yellow fluorescence under UV.
Optical Properties
Refractive Index: 1.542–1.551; Strongly Pleochroic (shifting between violet, blue, and yellow-grey depending on the viewing angle); Biaxial negative.
Hardness & Durability
Origin Region
Notable sources include India, Sri Lanka, Madagascar, and Brazil; found in metamorphic rocks and some igneous rocks.
Hardness & Durability
7 to 7.5 on the Mohs scale; fairly durable but brittle; susceptible to damage from hard blows due to cleavage.
Care & Maintenance
Clean with warm soapy water and a soft brush. Avoid ultrasonic or steam cleaners. Store separately from harder gemstones like sapphires.
Rarity & Value
Relatively abundant; value depends on the intensity of the blue/violet color and clarity. Usually eye-clean specimens are moderately priced.
Special Characteristics
Strong trichroism (pleochroism) is the most distinctive feature; often called 'Water Sapphire' for its blue appearance and clear shifting colors.
Lore & History
Historically known as the 'Viking's Compass' because it was supposedly used as a polarizing filter to locate the sun on overcast days. Often associated with the third eye chakra and inner vision.