THE MATERIAL LIBRARY
Iolite
The gem variety of cordierite.
Colors & patterns
Violet-blue, often showing grayer or paler colors from other directions.
Typical origins
Sources include India, Sri Lanka, Madagascar and Tanzania.
Hardness
7–7.5 on the Mohs scale.
Choosing & setting this material
Strong directional color is called pleochroism. Cutting orientation matters, and cleavage means the stone still needs protection from blows.
Care & cleaning
Clean gently with lukewarm water, a little mild soap and a soft cloth, then dry. Avoid steam, ultrasonic cleaners, harsh chemicals and sudden temperature changes, especially when treatments are unknown.
Origins above describe typical sources of the material, not the origin of an illustrated or stocked stone. Hardness measures scratch resistance, not resistance to breaking. Confirm the identity and treatments of the actual piece.
Further reading: Material reference · GIA: gem treatments