Question: What were the precious stones in the high priest’s garments and how are they related to the twelve tribes?
Answer: The ephod had two stones on its shoulder straps, both of onyx (shoham), with the names of six tribes inscribed on each stone (Ex. 29:9-12;39:6-7). As for the twelve stones in the choshen (Ex. 28:17-21;39:10-14), the Torah doesn’t indicate how they correspond to the twelve tribes; but the correspondence can be found in the commentary of Rabbenu Bachya:
Reuven – odem (ruby) Shimon – pitdah (smaragd) Levi – barekes (carbuncle) Yehudah – nofech (emerald) Yissachar – sapir (sapphire) Zevulun – yahalom (pearl) Dan – leshem (topaz) Naftali – shevo (turquoise) Gad – achlamah (crystal) Asher – tarshish (chrysolite) Yosef – shoham (onyx) Binyamin – yashfeh (jasper). The above translations of the gem names are from Ginsberg, Legends of the Jews, Vol.III pp.169-172. See also the article “Avnei Choshen ve-Ephod” in the Talmudic Encyclopedia.
All the Best, Rabbi Azriel Schreiber