In Hinduism, Rasalingam or Parad Lingam is a Lingam, the symbol of the god Shiva, made of mercury. Tamil Siddhas carved Shiva Lingam from solidified mercury. The process of solidification of mercury is the secret process enunciated by Tamil Siddhas. In Tamil, mercury is called Pada-rasam and the Shiva Lingam made using pada-rasam is called Rasalingam. In Sanskrit, mercury is called Parad and the Shiva Lingam made using parad is called Parad Lingam. Rasalingams or Parad Lingams are consecrated in Hindu Shiva temples, Ashrams and other places of worships.
Shiva puja must be performed with linga. Linga worship constitute the very essence of Shiva theology. The Shiva symbol linga is considered as formless. The Rasalingam has a place in the worship of Shiva. Although mercury comes under classification of a metal, it is in semi liquid form. Tamil Siddhas identified mercury as Shiva’s metal (Shivadhatu). According to Siddha alchemy, mercury is the representation of male (Shiva) form and the chemical element sulfur associated in the solidification process considered as the representation of female (Shakti or Gauri, consort of Shiva) form. There are various Siddha processes formulated in the solidification of mercury. The processes are painful and may require several hours and even days to complete. The resulting solidified mercury is enhanced with vital divine properties and it attain its very holy and beneficial effects when it is solidified and carved as Shiva Lingam. It is believed that the worship of Rasalingam or Parad Lingam promotes health and longevity.
Masilamaniswara Temple, Thirumullaivoyal
Kodiyidai Amman Sametha Masilamaniswara Temple is situated at Thirumullaivoyal, a small town forming part of west Chennai and the temple is 2 km away from Ambattur. The prime deity Shiva at this temple was incarnated by the hymns of Sundarar, Ramalinga Adigalar and Arunagirinathar. A Rasalingam is installed in the second corridor near sanctum sanctorum of Shiva. The huge Shiva Linga in the sanctum sanctorum is covered with sandal paste. Every year in the month of Chittirai(Mar-Apr), on Sadaya nakshatra(Sadayam star), the Santhana kappu (Sandal paste cover)is refurbished with Veru kappu. This is believed to be the treatment for the blood that oozed out of the deity because of the king's attack.
Shiva Temple, Vishakapatnam
Shiva temple is located in Visakhapatnam (also known as Vizag and Waltair), the second largest city in Andhra Pradesh. The temple is situated on Rama Krishna Beach road. The uniqueness of this Siva Temple is its Rasalingam, which is made of a 10 kg single stone.
Siddha Ashram, Ujjain
Siddha Ashram is located near to Harsiddhi Temple in Ujjain, Madhya Pradesh, India. The area contains a temple, meditation chamber and gardens, and attracts hundreds visitors seeking spiritual enlightenment each year.
The ashram is run by Acharya Mahamandaleshwara Swami Nardanandji who is known for his Kundalini Shaktipath initiation and research into ayurvedic based medicinal remedies. Siddha Ashram has consecrated the world’s largest Parad Lingam weighing about 1500 kg. during November, 2005. The Parad Lingam temple is located at Ashram complex. People are allowed to see, touch and worship this Lingam.
Dhyanalinga and Theerthakund, Coimbatore
The Dhyanalinga is a Yogic temple located 30 km (19 mi) from Coimbatore, India. Dhyanalinga temple was consecrated using prana prathista by Sadhguru Jaggi Vasudev, a yogi and mystic. The Dhyanalinga Yogic Temple offers a meditative space. It is dedicated for meditation
At this temple complex there is Theerthakund. Theerthakund is a subterranean tank located 35 ft (10.7 m) below holds a lingam immersed in water. Followers claim that the lingam is made of solidified and 99.8% purified mercury. People can take a dip in this water before they go to the Dhyanalinga temple. A semi-circular brick vault covers this tank, the inner sides of which have murals in pure natural dyes with its theme depicting a Maha Kumbha Mela scene.
Sri Dattashram, Anksapoor Village,velpoor mandal, nizamabad dist, Andhra pradesh
At Dattashram Anksapoor village near Nizamabad in Andhra Pradesh a Rasalingam, one of the huge rasalingam weighing about 411 kg. was consecrated on April 25, 2004 by the Jagadguru Pushpagiri Shankaracharya and Hampi Virupaksha Vidyaranya Peethadhipati. The Rs.6 lakh worth Rasalingam was brought from Banaras, Uttar Pradesh.it is a world largest rasalingam. anksapoor dattashram is a very powefull temple. it was very old temple. The was established by pujya sri vittal goud(bapu) maharaj. 
Paradeswar Temple in Dharamgarh
- "Linga". Encyclopedic dictionary of Puranas 5 (1st edition ed.). New Delhi: Sarup & Sons. 2001. pp. 1238–1243. Retrieved 2012-05-04.
- Parad Shiva lingam
- இரசவாதம் - ரசமணியும், ரசலிங்கமும்.
- மாசிலாமணி ஈஸ்வரர் கோவில், திருமுல்லைவாயில்
- Places of Worship in vizag
- Siddha Ashram (Website)
- Mercury Shivalingam of Ujjain
- Sadhguru Jaggi Vasudev: "Dhyanalinga: The Silent Revolution", Isha Foundation, 2000, ISBN 978-81-87910-00-8
- Rangaswamy and Sudhakshina. Transformation of the inner The Hindu 25 July 2003
- Sadhguru Jaggi Vasudev: "Encounter the Enlightened: Conversations with the Master", Wisdom Tree, 2004, ISBN 978-81-86685-60-0
- Huge Sivalingam draws crowds