From the reference from Skanda puran,vishnu puran,shiva puran,Devi bhagvad maha puran,kurma and Matsya puran etc.
shaligram is only found in gandaki river in nepal.
There are many kinds of Saligram such as smooth,round,oval,with chakra and without chakra mark.
Smooth shaligram is very good for worship. Black shaligram brings fame.a pale destroys sins,yellow bless a sincere son. red causes illness,rough create anxiety,crooked makes poor. Large shaligram takes away one’s duration of life,and worshipping shaligram shila without a chakra is useless. A brown salagrama sila mixed with other colors,a broken shaligram sila,as well as one with many chakras,one with only one chakra,one that has large mouth,one with big chakras,one with overlapping chakras,one with parallel chakras,one with broken chakra,one who has mouths towards the bottom,currtainly gives distress to devotees,