THE THIRD STONE IN THE BREASTPLATE OF JUDGEMENT IS THE CARBUNCLE GEMSTONE, REPRESENTING THE LEVI TRIBE [Hebrew: ("to join");Minäan "lawi'u" (= "priest")]
In ancient scripture, the Lord speaks through the prophet Malachi on His loving covenant with the tribe of Levi:
"Know then that I have sent this commandment unto you, that My covenant might be with Levi, saith the LORD of hosts. My covenant was with him of life and peace, and I gave them to him, and of fear, and he feared Me, and was afraid of My name. The law of truth was in his mouth, and unrighteousness was not found in his lips; he walked with Me in peace and uprightness, and did turn many away from iniquity."
A 13th Century Torah Commentary on the Carbuncle Stone
"The stone which bore the name of Levi was the ברקת, known popularly as carbuncle (a rounded gemstone without facets). It is so called as it flashes just like a bolt of lightning, ברק. It illuminates like a lamp. Onkelos also translates it as ברקן, a flashing stone. This was the gemstone Noach hung in the ark to provide him with light. The Torah referred to this light in Genesis 6,15 צהר תעשה לתבה. Isaiah refers to it as אקדח, in Isaiah 54,12 where, speaking of the future of Israel he writes: ”I will make your battlements rubies and your gates of precious stones, i.e. לאבני אקדח.” The name is justified as it appears glowing like red-hot coals. A similar expression occurs also in Isaiah 50,11: “kindlers of fire.” The reason this stone was chosen to symbolise Levi was that the Levites illuminate the people by teaching them spiritual illumination, i.e. Torah, as we know from Deut. 33,10 יורו משפטיך ליעקב ותורתך לישראל, “they teach Your judgments to Yaakov and Your Torah to Israel.” We also know of Moses, who was of the tribe of Levi, that the whole house was filled with light when he was born as the Midrash (Shemot Rabbah 1,24) interpreted the words in Exodus there (Exodus 2,2) that “she (his mother) saw that he was good.” Furthermore, when Moses returned from Mount Sinai with the second sets of Tablets the Torah testified that the skin of his face emitted rays of light (Exodus 34,29). We have another verse (Kohelet 8,1) “a man’s wisdom lights up his face.” The positive value of this gemstone is that it is apt to enlighten the foolish, providing him with insights he never had. This is in addition to the general usefulness of that jewel in providing light just as does a lamp. People say that if one pounds this carbuncle into fine dust and mixes it with food or drink as one mixes certain medicinal herbs into the food it proves very capable of providing wisdom and opening up previously “closed” hearts."
›קרא עוד › Shemot, Chapter 28:15,Torah Commentary by Rabbi Bachya ben Asher [13th Century], trans. Eliyahu Munk, 1998.