Shilajit is a blackish-brown exudation obtained from rocks in the Himalayas between altitudes of 1000-5000 meters. According to ancient Ayurvedic texts, it is a resinous substance secreted from mountainsides during the hot summer months. Shilajit comes in four varieties based on the metal from which it exudes - red, white, blue, and blackish-brown. The blackish-brown variety from iron rocks is considered the best. It is used in Ayurveda as a general tonic, stimulant, and aphrodisiac.