The Breastplate of Aaron is a prime example of how gemstones were used in spiritual practices of ancient times. The twelve stones in this ritual item were all supposedly crafted from different materials to represent the individual differences between each of the twelve tribes of Israel. Unfortunately, it is not clear from the original description of the breastplate found in Exodus what all twelve jewels were made of, as there are a number of ways to interpret the original Hebrew. Today, speculations can be made as to what these twelve stones were, but the original basis for evaluating which stones were used comes from the work of Titus Flavius Josephus.

Titus Flavius Josephus was a historian who lived in Jerusalem during the 1st century C.E. that took interest in the Priestly Breastplate, and attempted to determine what all twelve of the mounted jewels were made from. Josephus’ father was a member of the priestly class, and this may explain his interest in the Breastplate of Aaron. By this time the Old Testament had been translated from Hebrew (the Masoretic Text) to Greek (the Septuagint) and Josephus, doing something no one else had done before, used the comparison of these texts to inform his historical studies. Much like the struggles faced by today’s historians, Josephus clearly had difficulty developing what he thought to be an accurate list of gemstones, as he mentions the twelve jewels in his works Antiquities and Wars, but gives a slightly different list each time.

Not only does the work of Josephus help to illustrate what the twelve jewels of the Priestly Breastplate may have been, but many who came after him also posited their thoughts on the matter. Some of these later writers were other historians and some were religious philosophers. It is also important to consider what is known about the period in which the Priestly Breastplate existed from archaeological studies of the ancient world. For example, the size that the twelve jewels were said to be and the notion that each stone had been engraved on its front face can serve to help eliminate certain gemstones as possibilities given what is known about lapidary practices of that era.

The beliefs surrounding the Breastplate of Aaron offer an explanation for how all twelve jewels of the breastplate were crafted. In the Gemara, a section of the Talmud, is it said that the twelve stones in the Breastplate of Aaron were shaped using something called the ‘Shamir’ (ריִמׁש). From the descriptions of the Shamir, it is not clear whether it was a substance or some kind of worm-like creature, but it was believed to have the capability to cut through hard materials, including iron and diamond, and was said to have been used by King Solomon when constructing the First Holy Temple. It is possible that this substance was a form of the corundum-bearing rock emery (a.k.a. corundite), as emery has been mined and exported from the Greek isle of Naxos for well over two thousand years (at one point borrowing the island’s name as “Naxium stone”), and emery would have been hard enough to grind down any gemstone other than diamond.

Using Josephus’ work comparing the Hebrew names of the twelve jewels given in the Masoretic Text with the Greek names given in the Septuagint, along with the writings of later scholars and contemporary archaeological evidence, it is possible to gain a better understanding of which twelve gemstones were most likely set in the Breastplate of Aaron.

Click here to read Part 3 and learn more about the twelve jewels in the Breastplate of Aaron and what materials they may have been crafted from.