The mercury is liquid, its characteristic is that it gives its color on every metal. Whether its gold, silver, brass, copper etc. or any other metal. In Shiva Purana, mercury is said to be the semen of Lord Shiva. Shivaling is also made from many metals and woods and stones and gems. The most important is Parthiv Shivaling and Parad Shivaling which is made of Parthiv Shivaling soil and Parad Shivling is made by solidifying mercury liquid. By only touching the Parad Shivaling, many diseases get rid of it.