What is Saligram ?

Saligram is considered as a holy stones which is divine Symbol of lord Vishnu. The sacred Saligrama stones (black ammonite stone), are found only on the bed of river Gandak near Muktinath, Nepal. These naturally formed stones are used by devout Hindus to worship Lord Vishnu. It is not a stone-formation by nature. The chakras on the stones are formed by the river worms called Vajra-keeta. Its teeth/nails are said to be harder than granite stone. The chakra formation is found not only on the outer surface of the Saligrama. There are chakras inside Saligrama also. This can be seen through the hole or holes on the Saligrama with the aid of torch light. The holes are termed as vadana (mouth). Chakras can be seen inside these holes. At the very face of this chakra, one can confirm or suspect whether a particular Saligrama is original or duplicate.The Vajra keeta worms drill the stones, get inside and live there. During their stay inside the stones, they cause these chakras. Similarly outside Chakras also are caused by the worms only. Saligrama are used as living place by the worms not used as shells. The puranic declaration is that the Lord Himself causes these chakras in the guise of worms.
He reveals His presence in Saligrama through the Chakras. He is already present there by his own choice; we do not perform any pratishta-ritual for Saligrama just as we do for other idols.There are also some normal size, small and very small size Saligramas with no hole and no chakra. They look like mere black stones. But if you hold it against the lamp and look through the stone, you will be surprised to find it is transparent. That is, the reddish light will be visible inside the stone. These Saligramas are called Ratna Garbha.
Why these stones are called Saligrama?
That is due to a story in the Varaha Purana, which says that once there was a sage by the name Shalankayana, who was performing austerities and devotional meditation in many holy places with the view to gain a great devotee of Lord Vihsnu as his son. He visited the sacred tirtha (holy place) of Muktinatha in present day Northern Nepal, high in the Himalayas, and took his bath in the icy waters of the Kali Gandaki at the back of Annapurna Mountain. Extremely tired from his climb in the high altitude, he finally took rest under a sala tree. Fast asleep on the eastern side of the tree, he didn't notice that the Lord Krishna had come and stood before him. Then by the Lord's mercy the sage awoke and saw his Lord standing there and immediately propitiated him with melodious Vedic mantras. The Lord then fulfilled the desire of the sage and gave him a son on the spot, and being pleased with his devotional attitude, gave another boon.
Krishna informed that from that day (the dwadasi in the sukla paksa of the month of Vaisaka) He would eternally stay on the area of that mountain in the form of the Saligrama stone. Actually there was no sala tree there at that time - it was a special self-manifesting mercy incarnation of the Lord appearing for His devotee. So in the same way, the Lord continued to tell the sage that in the self-manifesting form of the Saligrama Shila He will reside there, and the devotees can take Him in this form and worship Him, and He will reciprocate their love in that way. This is confirmed in the Mahabharata (Vana Parva Ch 84, 123-125), where it is said the name Saligram is given to Lord Vishnu who resides in the Saligrama at the Saligram Tirtha.
In the Padma Purana Lord Siva declares the greatness of Saligrama Shila as follows:
Mallinga Kotibhi Drsthi Yad Phalam Pujiti
Saligrama Sila Yamtu Ekasyam Iva Tad Bhaved
The merit obtained by seeing and worshipping hundreds of thousands of My Lingams, is equivalent to that obtained by worshipping one single Salagram shila (stones).
If this is what Lord Shiva says, lets know where the Saligrama are found, what they are, their legend, types, Pooja and benefits etc.
Many types of Saligramas:
Saligrams are classified on the basis of its size shape, color, openings, chakras (natural carving), lines, weight etc. those popular types are as follows.
A. Lakshminarayana Saligram: Little dark in color, one mouth, four chakras and in one line.
B. Praddhyumna Saligram: Very little, one chakra on the top, and with crooked mouth.
C.Aniruddah Saligrama: Like a round ball, slightly yellow color, smooth and soft glasslike. It is believed it will brings peace and happiness.
D.Vasudeva Saligrama: It is equivalent to worshipping Krishna himself. It is rounding, shiny, with one opening mouth. It is surrounded by two chakras. It fulfills devotees’ wishes.
5. Sankarshana Saligrama: Two chakras facing each other. Narrow in the frontand wider at the back. For Brahmacharis, it brings knowledge.
6. Narasimha Saligrama: Worshipped with great devotion. Contains two chakrasand shape is varied. The devotee of this Saligrama becomes a sarva sangatyagi (renunciate) and a jitendria.
7. Lakshmi Narasimha Saligrama: Not a sugra as the Narasimha Saligrama. This Saligrama is thus an embodiment of pleasantness. This has a wide opening, has two chakra an also has a garland type of line .This brings to the devotees peace and solace.
8. Hayagriva Saligrama: Horse faced with two chakras. Not so appealing in appearance. Especially for gnanam (education).
9. Sudarshana Saligrama: Has an ordinary form with one Chakra.
10. Gadadhara Saligrama: Very ordinary with one chakra.
11. Madhusudana Saligrama: Dark cloud color and wheel shape. Has the sign similar to foot print of a calf. Very Holy.
12. Lakshminarayana Saligrama: One opening with a garland like line. color of dark clouds, four chakras. Very rare and special. Fulfils all desires of Bhaktas.
13. Lakshmijanardhana Saligrama: Same as above (12) but without garland shapeline.
14. Vamana Saligrama: Small in size, lighter shade of black colour, two chakras with no opening
15. Sridhara Saligrama: Same as above(14) but with a garland like line.Brings good luck and progress to the devotees.
16. Raghunatha Saligrama: Two openings, four chakras and a sign similar tofoot print of a calf.
17. Damodara Saligrama: Huge, found commonly in temples. Has two chakras.
18. RaNa Rama Saligrama: Round, moderate size, with two chakras, baby feet sign, bow and arrow signs.
19. Rajarajeshwara Saligrama: Same shape as above (17), but with seven chakras and the sign of an umbrella(Chatri). Brings Raja Yoga and RajaSanmanam to the devotees.
20. Anantha Saligrama: Pitch black with 14 chakras. Holiest of the Saligramas. Very rare.