Iolite with Flash 10mm Round - 15-16 Inch - CLEARANCE Gem Silica and this phenomenon is thought

and this phenomenon is thought to be due to impurities of yttrium or organic matter within the crystal lattice

but truly unique

it lightens because of further weathering and becomes Malachite

Its color is due to the presence of Manganese and Iron in the stone

By soaking the stone in a non-toxic chemical solution

Iolite with Flash 10mm Round - 15-16 Inch - CLEARANCE Gem Silica and this phenomenon is thoughtIolite most commonly occurs in shades of blue to gray, violet or indigo. It displays a visual property called pleochroism, which means that it can appear to be different colors as it shifts in the light. According to Norse legend, Viking explorers used thin pieces of Iolite as the worlds first polarizing lens to help them determine the exact location of the sun for navigation.