It is believed that apart from Parad Shiva Ling or Narmadeshwar Shiv Lingam no other form of Shiva Lingam should be worshipped at home.

According to ancient Hindu texts, it is believed that apart from Parad Shiva Ling or Narmadeshwar Shiv Lingam no other form of Shiva Lingam should be worshipped at home. The Parad Shivalingam, also called the Rasalingam plays a very important role in Lord Shiva’s worship. Tamil Siddhas consider mercury as Shivadhatu- Shiva’s metal. Mercury is said to represent the male (Shiva) form and Sulfur used for solidification process is considered as the female form (Shakti). It's said that by the very touch of this mercury a person gets the benefit of Shiv Puja done in all the three lokas. Although mercury classifies under metals, it is in semi liquid form. Therefore, a Shivling made of mercury is also known as Ras Shivling. Parad Shiva lingam is complete with 8 Sanskaars (8 stages of Purification according to Parad Sanmhita) and removal of Saptakanchuki (100% pure, medicated and hygienic); the Siddha Parad (Mercury mouth closed with Aghor Vidhya) is formed to make Murthi-Badhha / Agnibadha (heat resistant) Shiva lingam. It is said that worshipping the Parad Shivlingam gives 24 Ras and 5 Tatva which frees the body from all diseases!
Love, light & Blessings ~ Har Har Mahadev ~ Om Namah Shivaya!