Banalinga

A banalinga is a smooth ellipsoid stone found in the bed of parts of the Narmada River in Madhya Pradesh, India, which natural erosion has shaped to resemble a lingam, the aniconic form of the Hindu god Shiva. Hindus, particularly Shaivas and Smarta Brahmins, regard it as a manifestation of the god and call it svayambhu, self-born, because it is natural, not carved. The stones have a Mohs hardness of about 7. Their popularity has severely depleted the natural supply, and the stones sold commercially today are largely produced artificially. A banalinga is also one of the stones used in Panchayatana worship, the fivefold worship of Shiva, Vishnu, Devi, Surya and Ganesha, which Adi Shankara is said to have introduced.