Iolite is a gem quality form of cordierite, a magnesium iron aluminum cyclosilicate mineral. The name "iolite" comes from the Greek word for violet.The first significant discovery of large transparent, gem-quality deposits of iolite was made in 1996 by the American geologist, W. Dan in USA.

Iolite identification mark

Gem-quality iolite vary in color from sapphire blue to violet-like blue and from lightblue to yellowish-gray. Itshows strong pleochroism that can often be used to help distinguish iolite amongst other similar colored gemstones. Iolite can sometimes be mistaken for sapphire and tanzanite, but it is softer than sapphire, and harder than tanzanite.

Iolite origin

Most of the iolite gemstones available today come from India. Other significant sources are in Australia, Brazil, Burma, Canada, Madagascar, Namibia, Sri Lanka, Tanzania and the United States. The largest iolite crystal found weighed more than 24,000 carats, and was discovered in Wyoming, USA.

Iolite Hue

Gem quality iolite varies in color from sapphire blue to blue violet to yellowish gray to light blue as the light angle changes. From the top view down, it appears light golden or honey-yellow in color.

Iolite clarity and Surface

Fine gem-quality iolite appears transparent to translucent in clarity. Stones cut too deep may appear opaque. Most larger iolite stones exhibit some visible inclusions. Eye-clean specimens are rare. When polished, iolite exhibits an oily to vitreous luster.

Iolite care and cleaning

• Iolite is fairly hard and durable, but it shows good cleavage which adds to its fragility, therefore it should not be cleaned with heat steamers or ultrasonic cleaners.
• Use warm soapy water and a soft cloth to clean iolite gem.

Iolite gemological properties

Chemical Formula: Mg2Al3[AlSi5O18] Magnesium aluminum silicate

Crystal Structure: Orthorhombic; short prisms

Color: Blue, violet, brownish, yellowish, gray

Hardness: 7 to 7.5 on the Mohs scale

Refractive Index: 1.542 to 1.578

Density: 2.58 to 2.66

Cleavage: Good

Transparency: Transparent, translucent

Double Refraction: - 0.008 to -0.012

Luster: Vitreous

Fluorescence: None