Lapis Lazuli Jewelry

Where the name comes from: Latin lapis - stone, lazulum - sky or heaven.
Where the stones come from: Mined in Afghanistan for over 6,000 years, also found in the Andes, Lake Baikal, Siberia, Burma, India, Colorado and California.
Chemistry: A rock composed mainly of silicates, the blue color is due to the mineral lazurite which makes up 25-40%, (Na,Ca)₈(AlSiO₄)₆(SO₄,S,Cl)₂
Colors: Deep blue shades through to blue-purple and blue-green.
...and another thing: Ultramarine paint used by the old masters was ground-up lapis lazuli. It was by far the most expensive pigment often used for the most prestigious parts of a painting or even just used in some quantity in the picture to demonstrate the wealth of the owner.
 

Prices correct at time of writing - subject to change