The earliest witness to the entirety of the Old Testament is the Septuagint (LXX), dating to the third through first centuries B.C., during the Hellenistic period. This was translated into Greek from an earlier and now largely lost version of the Hebrew Bible. After the ca. 315 B.C. book On Stones by the Greek scholar Theophrastus, the LXX has more references to gemstones than any other surviving Hellenistic manuscript. A total of 22 gemstones are mentioned in 55 passages of the LXX. The objective of this study is to determine the geologic identities of these stones based on their descriptions in all available ancient textual sources that are contemporaneous (or nearly so) with the LXX and on the archaeological record of gemstones used in the Eastern Mediterranean/Western Asia region during the first millennium B.C.