Mercury is considered the sperm (seed) of Lord Shiva and in Ayurveda it is a flowing metalloid (fluid metal). There are 16 religious ceremonies to cleanse and harden mercury in chemistry. On account of being Lord Shiva`s sperm it is Lord Shiva - Incarnate.
"Ras Lingam Mahalingam Shiva Shakti Niketanam. Lingam Shivalayam proktam Sidhim wa Sarvadehinaam."-- The centre of Lord Shiva and Shakti are the Mercury Shiva Lingas known as Rasa lingas and are rare even for the gods to find.
In Indian cultural heritage, Mercury Shivaling holds a substantial position. It is written in Sarvadarshana Sangrah-
"Abhrakm tav beejurn tu mum beejurn to pardaha Baddho paardo lingo yam mritu daridrya nashnum"--Lord Shankar himself says to Bhagwati that the man who hardens Mercury in Linga and worships it, poverty would never enter his house and he would never dread death during his entire life.
Vidhay ras lingam yo bhakti yukta samarchwet Jagatray linganam pooja phalam mapnuyat Lingnam koti sahastrasya yatphalam samyagarchnat Tatphalam koti gunitam raslingam archanabhavet"--A man can achieve a thousand times superior blessing by worshipping a Shiva Linga, in case he venerates a Rasa Shivalinga or Parad (Mercury) Shiva Linga.
"Dharmarth kaam mokshakhya purusharth chaturvidya siddhayanti natra sandeho ras raj prasadtaha"
"Swayambhu lingam sahastra yatphalam samyagarchnat Tat phalam koti gunitam ras lingarchna bhavet"
There are four aims in human life - religion, health, desire and salvation. These can be satiated by worshipping the Mercury Linga and the worshipper of Lord Shiva receives uncountable amount of virtues.
It is stated in Brahma Purana that he who worships Mercury Shivaling with utmost devotion, irrespective of male or female, Brahmin, Kshatriya, Vaishya, Shudra, earns total materialistic pleasures, and lastly reaches supreme destination (redemption). During a mortal`s lifetime, they achieve magnificience, respect, high office, name and fame, sons, grandsons and excellence in learning. And, after all these perishable achievements, they attain redemption at last.
The virtue one receives by seeing the twelve Jyotirlingas is received merely by looking at one Mercury Shivalinga. The opportunity to look at it is possible only when the worshipper`s moralities of previous births become surfaced.
By worshipping Mercury Shivalingas, the worshipper receives the yields which are attained only by worshipping Shivalingas which are situated in three Lokas (celestial worlds).
Hence, Mercury Shivalinga, also called `Raseshwar Shivalinga`, possesses the greatest consequence from many view points, like religious and scientific.