Shalagrama shilas are used as
non-anthropomorphic representations of Vishnu alongside Dvaravati
shilas, similar to the use of yantra and kalasha in case of Devi &
linga and Baneshvara shilas in case of Shiva. The Pranatoshani Tantra
[8] states that worship of all deities can be conducted on a Shalagrama
shila. The Puranas unequivocally state that worship of Vishnu done
through a Shalagrama shila yields greater merit than that done through
an idol.
This is a Lakshmi Narsimha Shaligram. This shaligrams have teeth of narsimha on either sides (teeth visible inside of Shila).
According to Shastras, keeping Shaligram ji benefits the family in 6
dimensions: Noble way of life, Wealth, Protection from evil, good
health, worldly pleasures and blessing from Lord Vishnu .