Iolite?

Card	Iolite
Set	Gemstones
Edition	Unlimited
Book value	Est. 12 to 29 Credits once graded
Checklist	35 / 86
Rarity	Common
Owned	2

Iolite

Iolite is prized for pleochroism so strong that sailors are said to have used thin slices of it as a rough polarising filter to help locate the sun through cloud, one of the very few gemstones with a claimed practical use in navigation.