Diamonds in India are found in compact sandstones and conglomerates; either on the surface of these rocks or in the sands and gravels of rivers and streams that have flowed over them and have washed out these stones from their former situations. The annual worldwide output of Indian diamond-mines has been insignificant for centuries, and it is doubtful whether any appreciable number of diamonds leave the country at all. Just as it was before the eleventh century, mined diamonds are kept within the country to satisfy the passion for gems of the great Indian princes and magnates. Another reason these stones stay within the country is because their sales price is exceedingly higher in India, because in other world markets, the price of diamonds is regulated by the inexorable laws of supply and demand. So limited is the demand for diamonds in the Indian markets that the native supply is barely sufficient, and many foreign stones are imported, especially from the Cape in South Africa. Because India is not heavily involved with the worldwide diamond trade, not much is known of the recent quality of diamonds mined there. There are reports of single mines yielding stones of poor quality, but, as history gauges, India is a lush landscape of some of the world’s most prestigious diamonds. An Indian stone often shows a combination of luster, purity of water, strength of fire, and perfect "blue-whiteness" of color, and accounts of blue, green, and red diamonds have been heard of.