Deepest Blue Lapis Lazuli: this particular shade of blue is termed “ultramarine” and evidently takes its name for what the ancient Romans called Lapis Lazuli: “beyond the sea” which is, as far as the Romans were concerned, where the gemstone originated.
Crushed into powder and diluted, it is used to create a pigment for oil paintings said to be the most expensive, by weight worth more than gold in the Renaissance period, when its import into Europe from Afghanistan was controlled by the Venetians traders, who at the time were adept at controlling markets.
Afghanistan and Chile are the only two world commercial sources for Lapis, and of the two the Afghani material is consistently the better.
The Lapis in the above necklace is Afghani, natural untreated, and of a very high grade deep blue.