India once had many diamond mines and also mined sapphires, rubies & emeralds

diamonds everywhere..
Originally uploaded by Meghna Sejpal.

From the book, The Gems of Pre-British India by Manikant Shah

"Before the British came, India was a rich country and the fame of its wealth attracted both travelers and invaders. Minerals and Metals in Pre-Modern India by A.K. Biswas (2001) does give us a dazzling glimpse of this wealth, especially of the gemstones. The riches of India were mind-boggling indeed and Biswas tries to give a fair idea of its wealth. The British claimed that they came to 'civilise' India, but the reality was that they came to plunder its fabulous wealth and resources.

By the time of Shah Jahan, the treasury had a huge stock of diamond, emerald, lapis lazuli, ruby (some inscribed), sapphire and also rosary, necklace and ornaments studded with them."