At the end of the book of Job,after Job has prayed for his friends Job 42:10-11 it is written that each of Job's friends gave him a piece of silver and a gold ring, (NIV)
All his brothers and sisters and everyone who had known him before
came and ate with him in his house. They comforted and consoled him
over all the trouble the Lord had brought on him,and each one gave him
a piece of silver and a gold ring.
The Hebrew word that's translated as ring/earring is נֶזֶם (Nezem).
It can mean either ring, earring, nose ring, or generic ornament. I believe that the last translations translations are more correct, since there are places like Exodus 35:22 where נֶזֶם and טַבַּעַת (ring worn on a finger) are used in a single verse.
It seems that these nose/ear rings are often mentioned alongside with silver pieces, bracelets, rings, etc., in which case they just symbolize wealth.
I believe your question was "why did Job receive" the gold and I believe the answer is given in the text you cited:
All his brothers and sisters and everyone who had known him before came and ate with him in his house. They comforted and consoled him over all the trouble the Lord had brought on him,and each one gave him a piece of silver and a gold ring.
-- Job 42:11 NIV
The significance may be that his faithfulness in his ordeal was vindicated and rewarded, his fortunes restored.
8So take seven bulls and seven rams and bring them to my servant Job. And bring a whole burnt offering for yourselves and my servant Job will pray for you. I'll encourage him by not responding as your disgraceful folly deserves, since you didn't speak about me correctly as did my servant Job. 9So Eliphaz from Teman, Bildad from Shuah, and Zophar from Naamath did precisely as the LORD had spoken to them, because the LORD showed favor to Job. 10The LORD restored Job's prosperity after he prayed for his friends. The LORD doubled everything that Job had once possessed.
-- Job 42:8-10 NIV
It also serves as a good example of "pitching in" with tangibles for those who are down rather than just dumping pious words.
15If a brother or sister be naked, and destitute of daily food, 16And one of you say unto them, Depart in peace, be ye warmed and filled; notwithstanding ye give them not those things which are needful to the body; what doth it profit?
-- James 2:15-16 KJV
This has always been a sort of mystery that can only be solved by studying and meditating on the entire book.
My personal impression is that Iyov received a gold ring from each of his 7 brothers, who had abandoned him earlier:
Now all his brothers and all his sisters and all his previous acquaintances came to him and ate a meal in his house, and they bemoaned him and consoled him concerning all the evil that the Lord had brought upon him, and they gave him, each one one piece of money and each one one golden nose ring.
-- Iyov 42:11 The Complete Jewish Bible