05-21. Iolite – cordierite #1.
Iolite – or cordierite as the mineral is also called, is week #21 theme of this 52-week tour of the geometry of nature. The iolite crystal has an amazingly harmonious and well organized – antic tessellation – look and structure.
The name “iolite” comes from the Greek word for violet. The crystal comes in blue, bluish violet; greenish, gray to very pale blue in thin section. It is also called “water-sapphire” or “Vikings’ Compass” because Leif Eriksson and other Viking explorers used it to determine the direction of the sun on overcast days. It may qualify as the world’s first polarizing filter.
Its structure belongs to the dipyramidal, orthorhombic family.
The largest iolite deposits today can be found in Madagascar, Myanmar, Sri Lanka, India, and Brazil.
