[4] One of the earliest mentioned blue diamonds is the Hope Diamond, a 45.52-carat fancy dark grayish-blue which is believed to have been discovered in India but whose first recorded presence was in 1666 by French gem merchant Jean-Baptiste Tavernier, after whom it was called the Tavernier Blue.

[2][7] Most pure blue diamonds are Type IIb, meaning they contain either very few or a complete lack of nitrogen impurities.

Type Ia Blue stones contain a secondary hue and get their color from the presence of hydrogen.

[10] Since the 1950s, many methods have been developed to change a diamond’s appearance, including adding color to a colorless stone.

[12] The earliest recorded blue diamond, the Hope Diamond, was discovered in India, in the Kollur mine in the Guntur district of Andhra Pradesh (which at the time was part of the Golconda kingdom), in the seventeenth century.

[13][14][15] However, blue diamonds have also been discovered in the Cullinan Mine in South Africa and the Golconda region.

[16] It is thought that blue diamonds, unlike most other diamonds, are formed in the lower part of Earth’s mantle, and that the boron creating their blue color originates from serpentinite carried down to the mantle by subducting ocean tectonic plates.