Avraham's Jewel
Moshe Ben-Chaim
Understanding allegories literally is a grave mistake. The Rabbis of blessed memory composed metaphors and allegories to teach us many ideas in a concise format.
One such metaphor is the Rabbi's statement, (Baba Basra 16b) "Rabbi Shimon ben Yochai said, 'A precious stone was suspended on Abraham's neck(1), and any sickly person who saw it was instantly healed. And when Abraham died, G-d suspended it on the sphere of the sun." Literally understood, we cannot fathom how a stone can effect someone's health. However, taken as the Rabbis intended, as a metaphor, I offer an interpretation of "Avraham's jewel" which I feel makes more sense than taking it literally.
Avraham was known for teaching the ideas of monotheism to thousands of people. His speech was the tool used to direct masses in following the Creator. Perhaps the Rabbis meant that Avraham's speech, (allegorized as a jewel around his neck), cured incorrect notions among the masses. The Rabbis simply exchanged "speech" for the term "precious stone" as both are prized objects, and the "neck" is the source of speech. When Abraham died, his teachings continued through G-d's will, influencing many others to the reality of the Creator of the universe. This is described as G-d suspending the stone (Abraham's teachings) on the sun. This indicates that Abraham's teachings directed others towards the reality of the Creator of the universe, allegorized as the most dominant element in the universe, the sun.

Rabbi Bachaye (2) offered the same interpretation of the jewel, but suggested the hanging of the jewel on the sun after Abraham's death meant there were no others who spread monotheisim like Abraham. The sun alone attested to the Creator.

(1) This metaphor is also used by King Solomon in Proverbs, 1:9)
(2) Introduction to Parshas Yisro