The treatise On the Mixture and Power of Simple Drugs (Περὶ κράσεως καὶ δυνάμεως τῶν ἁπλῶν φαρμάκων) by Galen of Pergamum (129-216) is transmitted in a number of Greek manuscripts, and was translated into Syriac and Arabic. One Greek manuscript, Vatican Urbinas gr. 67, contains a passage from book IX about digamma and ‘Armenian earth’, not transmitted in the majority of Greek manuscripts and not included in the standard Greek edition by Kühn (1826). Galen called ‘Armenian earth’ a mineral that probably was orpiment, although the exact identification remains problematic. We now present a critical edition of the Syriac translation of part of this passage on the basis of the Syriac Galen Palimpsest; discuss the historic use of digamma; and explore the importance of Galen’s attestation of Armenian words.