Shila, (शिला in Devanagari, śila in IAST refers to a Vaishnava (Hindu) aniconic representation of Vishnu, in the form of a spherical, usually black-coloured fossil found in the sacred river Gandaki.  They are more often referred to as Shaligram Shilas, with Shila being the shortened version. The word Shila translates simply to 'stone' and Shaligram is a less well-known name of Vishnu. The origin of the name is traced to a remote village in Nepal where Vishnu is known by the name of Shaligraman. Shaligram in Hinduism is also known as Salagrama. The name Salagrama refers to the name of the village on the bank of Gandaki where the holy stones are picked up. The name is derived from the hut (sala) of the sage Salankayana, who beheld the form of Vishnu in a tree outside his hut (cf. Varaha-purana). This hut was on the banks of the Gandaki, and it was in that particular spot that these sacred stones were found in abundance. The stones were therefore called Salagrama.
The episode relates to 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 Gantaki 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 Salagrama 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 Salagrama 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 Salagram is given to Lord Vishnu who resides in the Salagrama at the Salagram Tirtha.
Although Hinduism is commonly represented by such anthropomorphic religious murtis, aniconism is equally represented with such abstract symbols of God such as the Saligrama. Furthermore, Hindus have found it easier to focus on anthropomorphic icons, as Lord Krishna said in the Bhagavad Gita, Chapter 12, Verse 5,
|“||It is much more difficult to focus on God as the unmanifested than God with form, due to human beings having the need to perceive via the senses.||”|
The Shilas (Ammonite fossils) are worshipped as manifestations of Vishnu Himself, identifiable from other stones by special markings which resemble Vishnu's paraphernalia such as mace, conch, lotus and disc (chakra). Narasimhadeva, Varahadeva and Vamanadeva are popular forms of worship. They are either black, red, or mixed in colour and are usually kept closed in a box and are only brought out for daily worship (puja). The Shilas are usually hereditary and are passed down through many generations, never being purchased or sold.
According to Vaishnava belief, the worshipper of a Shaligram Shila must adhere to strict rules, such as not touching the Shaligrama without bathing, never placing the Shaligrama on the ground, eating only prasad, and not indulging in bad practices. In most Vaishnava temples the main deity is usually decorated with a 'garland' mala, specifically an Akshamala, of 108 Saligrama Shilas.
Tulsi, also known as Holy Basil is closely associated with the origins of Shila worship.Once in anger Sarasvati cursed Lakshmi. Sarasvati's curse changed Lakshmi into a tulsi plant and forced her to live on earth forever. Vishnu, however, intervened and modified the curse, saying that Lakshmi would remain on earth as tulasi until the river Gandaki flowed from her body. In the meantime, He would wait by the riverside in the form of a stone to take her back to His abode. This stone was the Shaligram Shila, which thus remained on earth as a representative of Vishnu. The Shila Deities and the tulsi plant are thus always worshipped together as Vishnu and Lakshmi.
Historically, the use of Shaligrama (or Salagrama) Shilas in worship can be traced to the time of Adi Shankara through the latter's works. Specifically, his commentary to the verse 1.6.1 in Taittiriya Upanishad  and his commentary to the verse 1.3.14 of the Brahma Sutras  suggest that the use of Saligrama in the worship of Vishnu has been a well-known Hindu practice.
The largest and heaviest Shaligrama can be seen at the Jagannath Temple, dedicated to Vishnu, at Puri in Orissa. The main ISKCON temple in Scotland, called 'Karuna Bhavan' is famous for housing the largest number of Shaligram Shilas outside of India.
Puranic quotes on Shalagram 
With Keshava in the form of Salagrama shila reside all the devatas, asuaras, yaksas and the fourteen worlds.--- Padma Purana
The Lord resides in many places in which he may be worshipped, but of all the places Salagrama is the best.---Garuda Purana
Any person who has seen Salagram Shila, paid obeisances to Him, bathed and worshipped Him, has achieved the results of performing ten million sacrifices and giving ten million cows in charity.--- Skanda Purana – Hari-bhakti-vilas
“Any shila from the place of shalagrams can never be inauspicious though cracked, chipped, split in two though still in one piece, or even broken asunder.”--- Brahm Puran
“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.”--- Gautamiya Tantr
“Shalagramas do not require installation ceremony. When one begins the worship of shalagrama, however he should start with elaborate puja using all articles. The worship of shalagrama is the best form of worship, better than the worship of the sun.”--- Skand Puran
"Devotees should take the charanamrita mixed with Tulasi leaves from the shalagrama in their hand and sip it, sprinkling the balance on their heads.“---Gautamiya Tantr
“All those holy rivers awarding moksha, such as the Ganga, Godavari and others, reside in the caranamrita (bath water) of shalagrama.”--- Padm Puran
“Shalagrama should not be placed on the earth or ground and worshiped.”---Sammohan Tantr
“In puja of shalagrama it is unnecessary to call the Lord for worship or request Him to return His abode upon completion.”--- Bhagavata Purana
“It is impossible to fully explain the importance of Tulsi leaves (Holy Basil) in the worship of shalagrama, as Tulsi is the most beloved consort of Hari in the form of shalagrama.”--- Brihan-naradiya Purana
“He who takes the charanamrita of shalagrama destroys all sinful reactions at their roots, even the killing of a brahmana.”--- Skand Puran
“By taking the remnants of foodstuffs offered to shalagrama, one will get the result of performing many sacrifices.”--- Skand Puran
"One who has dranked the water that bathes a Shaligram at least once in life time won't have to suck his mother's breast for the second time. He has attained Moksha (liberation)" --- Skanda puran
Sale and purchase of Shalagrama-shilas prohibited 
The Skanda Purana warns that no one should buy or sell shalagrama-shilas. One who puts a price on a shalagrama-shilas, sells a shalagrama-shila, gives his opinion on its value, or examines one with a view to estimate its sale value, all such people will live in hell until the time of universal destruction.
The marks made by the shell of the ammonite give a Shaligram its characteristic appearance, with the pattern often resembling and representing the 'Sudarshan Chakra' or the discus with a sharp-toothed edge which rests on the index finger of Lord Vishnu. Shaligram stones come in dfferent colors such as red, blue, yellow, green and black. Of these, the yellow, blue and black varieties are considered more sacred. The yellow and golden-colored Shaligrams are considered most auspicious and are believed to bestow great wealth and prosperity on its worshippers. Some Tips and Importance of Shaligram Shila's are given below:
- Worship Shree Shaligram for six values of life:Righteous living, Wealth, Protection, good health, pleasures and Spiritual .
- The Shaligram is the most sacred stone worshipped by the Vaishnavas and is used to worship Vishnu in an abstract form i.e., God without form as a 'Saligrama'. The use of the Shaligram is similar to the use of 'Lingam' as abstract symbol of Lord Shiva.The Shaligram is found in river Gandaki near Muktinath in Nepal.
- There are numerous popular beliefs concerning Salagrama. Salagrama alongside Tulasi leaves and conch (samkha), placed in one plate is regarded as most meritorious.
- Any religious observance, gift, consecration, obsequies, and worship should preferably be done in association with a Salagrama.
- Regarding the obsequies or the last rites (sraddha), it is usual to conduct such ceremonies in front of a Salagrama. For that would ensure the departed spirit reaching Vishnu’s abode directly: and subsequent death ceremonies would become unnecessary.
- When the dying person is made to sip a little of the water in which the Salagrama-stone is bathed, he will be freed from all sins, and will reach the heavenly abode of Vishnu. And death itself when it occurs in the presence of a Salagrama-stone will pave the way for Vishnu’s realm, for Vishnu is present in that stone.
- The rites of expiation of sins (prayaschitta) becomes effective more by drinking the water in which these stones are washed than by gifts or fasting or by observances of various kinds.
- In times of solar or lunar eclipse, whatever ritual is undertaken becomes all the more effective when done in front of a Salagrama-stone so says Hemadri.
- It was practice in the olden days to ask the witness to hold a Salagrama in hand while testifying in a court of law; if he uttered utter falsehood, he was believed to suffer immensely and long as a punishment.
- Merely looking at a Salagrama stone would wash away the sins of the beholder, even as the mere sight of a lion would make the antelopes run for their lives in the forest.
A Shaligrama - which has the marks of a shankha, Chakra, gada and padma arranged in a particular order - is worshiped as Keshava. With the change in the order of the four symbols, the name of the Shaligrama stone is also different and the images of such deities also have similar setting of the four symbols. The various orders and names are given for the twenty four permutations. These are well known names, which are the different names by which Lord Vishnu is known in the Hindu pantheon. The various versions of the Saligrama Shilas or stones vis-a-vis the order of the four symbols are:
- Shanka, chakra, gada and padma - Keshava
- Padma, gada, chakra, shanka - Narayana
- Chakra, shanka, padma and gada - Madhava
- Gada, Padma, Shanka and Chakra - Govinda
- Padma, shanka, chakra and gada – Vishnu
- Shanka, padma, gada, chakra – Madusudhana
- Gada, chakra, shanka and padma – Trivikrama
- Chakra, gada, padma, shanka - Vamana
- Chakra, padma, shanka, gada - Shridhara
- Padma, gada, shanka, charka - Hrishikesh
- Padma, chakra,gada, shanka - Padmanabha
- Shanka, chakra, gada, padma - Damodara
- Chakra, shanka, gada, padma - Sankarshana
- Shanka, chakra, padma, gada - Pradyumna
- Gada, shanka, padma, charka - Aniruddha
- Padma, shanka, gada, chakra - Purushottama
- Gadha, shanka, chakra, padma - Adhokshaja
- Padma, gada, shanka, charka - Narasimha
- Padma, chakra, shanka, gada – Achyuta
- Shanka, chakra, padma, gada - Janardana
- Gada, padma, shanka, chakra - Upendra
- Chakra, padma, gada and shanka – Hari
- Gada, padma, chakra and shanka - Krishna
- Shanka, charka, padma, gada – Vasudeva
See also 
- Shaligram: "The Divine Gift"
- :Shaligram and astrology
- Hinduism: Beliefs and Practices, by Jeanne Fowler, pgs. 42-43, at Books.Google.com and Flipside of Hindu symbolism, by M. K. V. Narayan at pgs. 84-85 at Books.Google.com
- A. Mahadeva Sastri. Taittiriya Upanishad: with the commentaries of Sankaracharya, Suresvaracharya, and Sayana (Vidyaranya), pp. 80 (free download at: http://www.archive.org/download/taittiriyaupanis00sankiala/taittiriyaupanis00sankiala.pdf)
- "Taittiriya Upanishad", Chapter 1, Section 6, Verse 1 in Complete Works of Adi Sankara, Department of Computer Science and Engineering, Indian Institute of Technology, Kanpur (url: http://www.sankara.iitk.ac.in/sbha.php3?toption=3)
- George Thibaut. The Vedanta-Sutras with the Commentary by Sankaracarya: Sacred Books of the East, Volume 1, pp. 178 (url: http://www.bharatadesam.com/spiritual/brahma_sutra/brahma_sutra_sankara_34083.php)
- "References collected by Padmanab Goswami from Hari Bhakti Vilas". Retrieved 2009-07-13.
- "Ancient Astrological Gemstones & Talismans by Richard Shaw Brown". Retrieved 2009-07-13.
- Debroy, Bibek; Dipavali Debroy. "The Garuda Purana". Shalagrama (Lulu.com). p. 42. ISBN 0-9793051-1-X. Retrieved 2009-12-21.
- Rarest of Rare Shaligrams
- Darshan of Rare Shaligram Shilas
- Articles about shaligram
- Website for information on Shaligram Shilas
- Information about Shaligram Shilas
- Shaligram Mantra & Mul Puja Vidhi
- Simplified Shalagram Worship