The story of the Syamantaka Gem is from the Srimad Bhagavatham which again contains a lot of stories on the life of Lord Krishna.
In Dwaraka, there lived a Yadava nobleman by name Satrajit. He was an ardent devotee of Lord Surya and propitiated Lord Surya regularly with great devotion. One day Lord Surya was overwhelmed with Satrajit’s devotion that He appeared in person to him in a dazzling form and gifted Satrajit with the jewel He was wearing. The gem was none other than the SYAMANTAKA GEM. This Gem was supposed to be a force to ward off natural calamities and keep the owner very prosperous. Everyday in the morning the Gem produced lots of Gold coins. Satrajit was very happy and kept the Gem with great devotion in his altar and worshipped it. He would distribute the gold coins everyday to the needy and thus everyone was becoming prosperous.
Lord Krishna who also lived in Dwaraka came to know of the Gem and thought that such a treasure would be safer in the hands of the king. He also felt that it was only proper for wealth to be in the custody and command of the king of the place. So he asked Satrajit to keep the gem in the custody of the king. Satrajit was not willing and felt that it was not Krishna’s business. Lord Krishna left it at that.
Now, Satrajit had a brother by name Prasenjit who was very fond of hunting. One day, Prasenjit, while going for hunting wanted to wear the Gem on his person. Satrajit gladly gave it to him. Prasenjit hung the gem as a pendant in his chain and went to the forest. While hunting in the forest, he had an encounter with a lion and died. The lion was enchanted by the Gem that it pulled it along with the chain and was carrying the same, when it came face to face with Jambavan. Jambavan was the mighty bear who had helped Lord Rama in the previous Yuga, while Rama went to recover Seetha from the clutches of Ravana who had carried her there. After the period of Lord Rama, Jambavan who has the gift of being a Chiranjeevi, (that is to live for ever) was living in one of the caves in the forest there with his extended family. Jambavan, when he saw the Gem with the chain being carried by the lion, was so fascinated with the dazzle of the gem that he struck the lion dead and carried the jewel to his cave. The little bears in his cave, his children and grandchildren were equally fascinated by the gem and they took it as a toy.
Days passed and Prasenjit did not return to the palace. A search team was sent to the forest but they returned empty handed. Satrajit was worried. He started suspecting Lord Krishna of kidnapping and killing his brother as Krishna had shown interest in the Gem. Lord Krishna was deeply perturbed when he heard about Satrajit’s thinking. He was determined to find Prasenjit and the Gem.
Krishna took about ten people and went into the forest. After a few days, they found Prasenjit’s body but with the Gem missing. They also found the pug marks of a lion. They followed the pug marks and at a distance, found the dead body of the lion. It appeared that the lion had been hit by an animal with sharp claws. And then they noticed the marks of the bear. They started following the marks of the bear’s paws and it led them to a huge cave at a distance. Krishna surveyed the cave from outside and told his team to wait under a tree while he went inside.
Slowly and stealthily, Krishna entered the cave, when he saw a little bear toying with the Syamantaka Gem at the entrance. He had to get the gem without disturbing the bear. Such thoughts racing in his mind, he waited behind a crevice near the entrance in the cave till the little bear turned aside. Just as he was about to pick up the gem which lay on the ground, the little bear turned around and gave out a startled grunt. Hearing the grunt, Jambavan rushed out from inside. He was completely shocked at the stranger in his cave and without even talking to him, came to attack him. Lord Krishna was ready and took him on. First they fought with knives, then with stones. Then they uprooted trees and fought. “This stranger is so strong”, thought Jambavan and decided to wrestle barehanded with him. Krishna was ever ready and the fight lasted for over ten days. The people outside was worried as Lord Krishna had not returned yet.
Jambavan started worrying. Nobody had fought with him so tirelessly and who was this stranger with so much strength? It was then that Lord Krishna appeared to Jambavan as Lord Rama. “Alas!! what have I done” thought Jambavan as he fell flat at the Lotus feet of his Lord. He was filled with deep remorse as he started worshipping Lord Krishna repenting all the while at his thoughtless fight. He enquired on Lord Krishna’s mission and gave him the Syamantaka Gem and honoured the Lord with a variety of fruits and delicacies. He also requested the Lord that his daughter be accepted as a wife by the Lord and so Jambavati was married to the Lord.
Krishna returned to the town with his retinue, the Gem and Jambavati. He gave back the Gem to Satrajit and informed him of Prasenjit’s death. Satrajit was truly ashamed of having suspected Lord Krishna and as a token of gratitude to the Lord offered the hand of his daughter Satyabhama to the Lord and so, the Lord married Satyabhama.
This is the story of the Syamantaka Gem.
It is said that Lord Krishna had looked at the moon on a Chaturthi day , and it is because of that he suffered this blame. This is linked to the story where Ganesha curses the moon for mocking at his figure and said that whoever saw the moon on a chaturthi day would have to undergo sufferings and blame!