Iolite Jewelry

Where the name comes from: Greek ion - violet.
Where the stones come from: Many places worldwide, notably India, Sri Lanka, Mozambique, Zimbabwe, and Brazil.
Chemistry: Magnesium iron aluminium cyclosilicate, (Mg,Fe)₂AL₄Si₅O₁₈ 
Colors: Blue through violet, greenish, yellowish brown to grey and colorless. Crystal appear different in color when observed from different directions.
...and another thing: Viking explorers used thin pieces of iolite as polarizing filters to be able to determine the position of the sun so aiding their navigation.
 

Prices correct at time of writing - subject to change