Cordierite, or Iolite, has several names, including Water Sapphire because of its naturally delicate, changeable, watery colors, remiscent of the changeable ocean. Iolite is a natural color change gemstone, going from cornflower blue to taupe to navy to violet blue, and other shades, depending on the angle the light hits, and of course, the stone itself. This color change property, called dichroic when two colors are involved, and pleochroic when there are multiple colors, is a rare phenomenon, and on account of its rarity, often makes a gemstone more valuable. Very little cordierite is actually fit for use as a gemstone. The priveliged pieces that make the grade are usually called iolite or water sapphire. The word "iolite" actually goes back to the Greek word for violet.

Iolite is sometimes used in place of sapphire, but is a slightly softer stone, being a 7-7.5 on the Mohs scale, compared to the 9 of corundum, which includes blue sapphire.

The vast majority of cordierite, though unfit for gemstones, has many other uses. It is often used in industry. One common use of cordierite is, in fact, in the catalytic converter for your automobile, where the stone can be arranged so that thermal shock does not cause the converter to crack. But that's not the first use of iolite in business. Much more historic is the use of the iolite stone by the Vikings in navigation because it changes, even on cloudy days, & so was used to determine direction when the sun was hidden behind clouds. That led to yet another name for this awesome stone: Viking's Compass.

Respect the rock! You are not getting just a pretty jewel, but a rare item with some fascinating background! Cool, huh?