The 'Golconda Blue', a rare historic Indian diamond, is set to make its auction debut at Christie's 'Magnificent Jewels' sale in Geneva. The 23.24-carat blue diamond, mounted in a ring by celebrated Parisian designer JAR, is expected to fetch an estimated $35-$50 million (₹300-₹430 crore). It was once owned by Yeshwant Rao Holkar, the last Maharaja of Indore, said Christie's.