What the scriptures say about Saligramas

Padma Purana:

Salagrama Sila Rupi Yatra Tisthati Kesavah |
Tatra Devasurayaksa Bhuvanani Catur Dasa ||

With Keshava in the form of Salagrama Sila reside all the devatas, asuaras, yaksas and the fourteen worlds.

Lord Shiva further declares that, "My devotees who offer obeisances to the shalagrama even negligently become fearless. Those who adore me while making a distinction between myself and Lord Hari will become free from this offence by offering obeisances to shalagrama. Those who think themselves as my devotees, but who are proud and do not offer obeisances to my Lord Vasudeva, are actually sinful and not my devotees. O my son, I always reside in the shalagrama. Being pleased with my devotion the Lord has given me a residence in His personal abode.
Giving a shalagrama, is the best form of charity, being equal to the result of donating the entire earth together with its forests, mountains, and all.

The Garuda Purana describes the glories of keeping a shalagrama-shila with the
auspicious mark of a cakra in one's house.
Ato'dhisthana Vargesu Suryadisviva Murtisu |
Salagrama Silaiva Syad Adhisthanottamam Hareh ||
The Lord resides in many places in which he may be worshipped, but of all the places Salagrama is the best.

Skanda Purana - Haribhakti vilas
Drstva Pranamita Yena Snapita Pujita Tatha |
Yajna Koti Samam Punyam Gavam Koti Phalam Bhavet ||

Lord Siva spoke to Skanda, his son, saying that any person who has seen Salagram Sila, paid obeisances to Him, bathed and worshipped Him, has achieved the results of performing ten million sacrifices and giving ten million cows in charity.

Pujito'ham Na Tair Martyair Namito'ham Na Tair Narah |
Nakrtam Martya Loke Yaih Salagram Silarcanam ||

(Lord Siva speaks to his son, Skanda) In this mortal world, if anyone does not worship Salagram Sila, I do not at all accept any of their worship and obeisances.

Brahma Purana the Supreme Lord Vishnu states that any shila from the place of shalagramas can never be inauspicious though cracked, chipped, split in two though still in one piece, or even broken asunder.

Lord Shiva also confirms in the Skanda Purana that even if a shila is cracked, split, or broken it will have no harmful effect if it is worshiped with attention and love by a devotee. It further states there that the Supreme Lord Hari, along with His divine consort, Lakshmi, live in the shalagrama that has either the mark of a chakra, a chakra along with the mark of a footprint, or a mark resembling a flower garland.

Gautamiya Tantra States that merely by touching a shalagrama one becomes freed from the sins of millions of births, so what to speak of worshiping Him! By shalagrama puja one gains the association of Lord Hari.