mineral

Tumbled iolite (water sapphire)

Iolite; cordierite, (Mg,Fe)₂Al₄Si₅O₁₈

AI-generated identification · may be incorrect

Hardness 7–7.5 Mohs; typically blue-violet with gray, white, or yellowish areas, vitreous luster, and orthorhombic crystals. Strong pleochroism produces blue-violet, gray, and pale yellow views; this small piece appears tumbled or polished.

Identified August 30, 2026More mineral →

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Physical properties

Formation & geological history

Forms mainly in aluminum-rich metamorphic rocks and granitic pegmatites through high-temperature metamorphism, commonly associated with mica and quartz. Cordierite deposits range from Precambrian to younger Phanerozoic terrains.

Uses & applications

Transparent blue material is cut as a gemstone; opaque or heavily included pieces are sold as cabochons, tumbled stones, or specimen material. Common uses are ornamental and lapidary rather than industrial.

Geological facts

Iolite’s name derives from Greek for “violet,” and its pleochroism historically helped navigators orient thin slices toward the Sun. It is sometimes marketed as “water sapphire,” although it is not sapphire.

Field identification & locations

Identify it by blue-violet coloration, strong pleochroism, moderate hardness, and lack of sapphire’s higher hardness (9). Important sources include India, Sri Lanka, Madagascar, Brazil, Tanzania, and Norway; visual identification is tentative from a photograph.