Iolite
Other Silicates & Gemstones
Iolite is transparent gem-quality cordierite, a magnesium-iron-aluminium silicate. Its strong pleochroism can show violet-blue, pale blue, and yellowish or nearly colorless directions in the same stone.
Identity
- Material or variety
- Cordierite
- Scientific or material identity
- Cordierite (iolite variety)
- Classification
- Natural mineral or mineral variety
- Aliases or trade names
- Cordierite · Dichroite · Water sapphire
- Composition or formula
- Mg₂Al₄Si₅O₁₈
- Crystal system or structure
- Orthorhombic
- Geological or manufacturing origin
- Can form in more than one geological environment, or combines several materials.
- Mohs hardness
- 7 to 7.5
Origins
India · Madagascar · Sri Lanka · Tanzania
Appearance & optical properties
violet-blue pleochroic cordierite.
History & discovery
The name iolite comes from the Greek word ios, meaning violet. Mineralogical cordierite was identified in 1813 and named for French geologist Louis Cordier. Stories describe thin iolite slices as Viking navigation filters, but GIA presents that use as legend rather than established fact.
Uses & care
- Common uses
- Transparent iolite is faceted or cut as cabochons for jewelry, especially pieces protected from heavy wear.
- Handling and cleaning
- Clean with warm soapy water. Avoid steam, ultrasonic cleaning, high heat, sudden temperature changes, and sharp blows, because one perfect cleavage direction makes the gem vulnerable to splitting.
Jewellery
5 pieces of Iolite jewellery. Learners earn each one in DigMyGem by learning words; until then it shows as a silhouette.
Viking Compass Pendant
Pendant
A thin polished slice of iolite, the stone said to have guided Norse sailors to the sun through cloud. It hangs in a silver ring so it can be turned to the light and flash from violet to clear.
Iolite Shield Ring
Ring
A step-cut iolite the violet-blue of a cold sea, set in a broad shield-shaped silver ring. The cutter had to turn the rough to catch the blue and not the yellow.
Voyager's Violet Necklace
Necklace
A necklace of graduated iolite drops that shift from blue to violet as they move, like the northern lights over still water. Each stone is held in a slender claw so the light passes through.
Water Sapphire Brooch
Brooch
An imagined brooch of iolite, once called water sapphire. Turned in the hand, the stone changes from violet-blue to pale grey.
Norse Sea Tiara
Tiara
An imagined silver tiara shaped like a longship's prow and waves, set with violet-blue iolite, the water sapphire.