The Vishnu Purana and the Bhagavata describes the story of Syamantaka Mani. The precious stone or the Syamantaka Mani originally belonged to the Sun god or Surya who wore it around his neck. It was said that whoever possessed this jewel would never come across any mishaps in the form of natural disasters like in the form of droughts, floods, earthquakes or famines, and would always be in prosperity and opulence. It is also said that wherever the Syamantaka Mani is kept, it would produce almost nine mounds of pure gold daily for the keeper. This gem is also the basis of the stunning light and rays of the Sun god.
There was a king of the name Satrajit, a Yadava nobleman. He was a great devotee of the Sun-god or Surya. Satrajit while walking along the sea shore was praying ardently to Sun-god. Sun-god pleased with Satrajit's devotion himself appeared and stood before him. Seeing the god in an indistinct and dazzling fiery shape, Satrajit asked him to appear in a less blinding form, so that he could see the God clearly. On this the Sun god took the Syamantaka jewel off his neck, and Satrajit saw the Sun God who is of a dwarfish stature, with a body like burnished copper, and with slightly reddish eyes.
Sun-god awarded Satrajit as a blessing, the precious gemstone Syamantaka Mani. As a consequence of this Syamantaka jewel, when Satrajit returned to Dwaraka with the jewel, people mistook him for the Sun God himself, such was his dazzling glory.
Satrajit later presented Syamantaka Mani to his brother Prasena, who was also the ruler of the Yadava region. Prasena used to wear the gem often, and once while walking in the woods with it, he was attacked by a lion, which killed him and fled with the jewel. Then the lion was attacked by Jambavan, described as a 'bear', killed it after a fierce fight and took the Syamantaka jewel. Jambavan was in Rama's army of monkeys to Lanka.
It was rumoured that Lord Krishna wanted to possess Syamantaka Mani or jewel. Thus when Prasena did not return, people started to accuse Krishna for the murder of Prasena and for the theft of the precious stone. With the purpose to prove his innocence, Krishna wanted to find out the true offender and recover the Syamantaka Mani. As he followed on the search of the dead Prasena, Krishna came to the place were he found the dead body of Prasena and his horse. He also found the pieces of teeth and nails of a lion. Krishna then followed the footsteps of the lion, which led him to the spot of the second struggle, were the corpse of the lion was lying. From there, he followed the tracks of a bear, which finally led him to the entrance of Jambavan's cave. In that cave Jambavan's children were playing with the Syamantaka Mani. Jambavan entered the cave and found Krishna; he thought him to be an intruder and wanted to kill Krishna. There was a combat between Krishna and Jambavan that lasted for twenty-one days, defeated him, got back the Syamantaka Mani, and returned to Dwaraka. Krishna later married Jambavati, Jambavan's daughter.
In the meantime Krishna's family members and friends waited for twelve days outside the cave but Krishna did not came out and they thought that he was dead. All of Krishna's friends and family members became extremely grief-stricken and started worshiping Goddess Durga to assure the Lord's safe return. As they performed this worship, Krishna entered the Dwarka with his bride Jambavati.
Krishna then called Satrajit to the royal assembly and, after recounting to him the entire story of the Syamantaka jewel's recovery, gave the gemstone back to him. Satrajit did not want to take the jewel but Krishna forced him to take. Satrajit accepted the jewel, but with great shame and remorse. He went back to his home, and there he decided to offer Lord Krishna not only the jewel but also his daughter, Satyabhama. Sri Krishna accepted the hand of Satrajit's daughter, Satyabhama, who was endowed with all divine qualities. But Krishna refused to take the jewel and returned it to King Satrajit.
Some days later, Krishna and Balarama were going towards Hastinapur after hearing the rumours that the Pandavas have been burnt to their deaths in a fire. In the mean time Kritavarma, Akrura and Satadhanwa, wanted to steal the Syamantaka Mani from Satrajit. Thus in Krishna's absence from Dwaraka Satadhanva at one night entered the house of Satrajit and murdered him to death and stole the jewel.
Satyabhama was mournful and rushed to Hastinapur to inform Krishna about the horrifying death of her father Satrajit. Krishna and Balarama immediately started for Dwaraka to avenge Satrajit's death, hearing of which Satadhanwa fled on his horse, keeping the jewel with Akrura. Satadhanwa was chased down by Krishna and Balarama and finally killed by Krishna near Mithila. Later Krishna returned to Dwaraka, and upon realizing that Akrura had already fled to Kashi with the Syamantaka jewel, summoned him up, and asked him to admit his guilt. When Akrura obeyed what Krishna had said then He let him keep it, on the clause that Akrura had to stay in the city of Dwaraka.