The name indicolite which mineralogists give to these blue stones suggests the indigo-blue color which they afford.    From Wordnik.com.  [A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public] Reference

Gem-blue indicolite crystals don't normally exceed 2 or 3 inches in length; these are 12 inches, possibly the largest in the world.    From Wordnik.com.  [In Pictures: Highlights Of Marc Weill's Mineral Collection] Reference