Iolite

Posted on August 31, 2017 by John J. Bradshaw, GG (GIA)

INTRODUCTION Iolite is the trade name for gem quality cordierite, a mineral species in the orthorhombic system, with the formula, (Mg,Fe)2AL4Si5O18. Cordierite has been known for hundreds of years and was named in 1813 after…

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