Salagramam as they are called and not Saligramam.
Salagrama silas are worshiped as Mahavishnu in his various forms – Varaha, Narasimha, Sudjarsana, Masya, etc. etc. Wherever Salagramams are there, it is worshiped as a temple. If 12 Salagramams are kept in a house it is equal to 1 diyadesam temple. But as mentioned it requires Nithya Aradhanam and one has to follow strict and orthodox rules and regulations. Just for the information, the moola murthy at (one of the 108 divyadesams) Trivandrum Anantha Padmanaba Swamy temple is made of 12,000 Salagramam brought from Nepal and there is a please called Thiruvattar ( another divyadesam) which is around 50 kms from Trivandrum – the moola murthy is made up of 18,000 Salagramams and the deity is called Adhikesavan and one would be astonished to hear that this deity has his tradition that he came into existence even before the birth of Brahma, as there is no Bhrama seen from his Nabikamalam.
The legend goes like this : one lady devotee Gandaki (also referred to Tulsi who cursed Lord Mahavishnu to become stone) did deep penance towards Lord MahaVishnu and happy with that Lord gave her a boon that he will reside in her womb. This lady took the form of Gandaki river and Mahavishnu resides there in form of Salagrama silas. These a type of black stones and an insect called Vajra Kreeta lives within that and carves different chakars and marks. Based on these marks the Salagramam identified with specific deity.
One can visibly see the Panchayuthams of Maha Vishnu – Changam, Chakram, Dhanush, Gadha (maze) and Kadkam (sword) on some silas or only chakram or dhanush as the marks. If you take Narasimha sila, you can clearly see the big mouth opening like a lion with its fangs.
This place which is one of the 108 divya desam is called as Mukthinath and is located in Nepal.. One has to travel to the Indian border near Gorakpur and travel from there to a place called Pokra. From Pokra to Jomsom by air and Jomsom to Muthinath by air or bike or jeep one can reach this temple amids snow covered Himalayan mountain terrain.
One cannot forget this experience throughout his / her life time. One can go on writing about this place pages after pages and it will never end.
ABOUT SALAGRAMAM :
It is related to a naturally formed stone like substance, believed to be of the "Amsa" or part of Lord Mahavishnu.
Vaishnavaites consider it very sacred and holy. They worship " Salagramam". (In Marathi, there is a surname, " Salagram". It may have something to do with the " Salagramam " I am discussing here.)
Some families inherit this " Salagramam" from their forefathers and ancestral lineage. Such ancient " Salagramams are considered to be very auspicious.
Only an expert in " Saligramam " can identify a genuine and natural one. There are sellers, dispensing fake stones as Saligramam.
Saligramams originate in the " Gandaki " river in
Nepal, in the Himlayan ranges.
Caution : As Saligramam is considered to be very pious and sacred, its worship can be done only by those who are extremely sincere in its worship. It has very rigid rules and traditions. So if one wishes to attempt worshiping a Saligramam, kindly consult an experienced person who worships it or an expert.