In this talk I track how the language of Middle English poetry densifies around pearls and becomes precious—precious in both senses of the word: on the one hand, rare and valuable; on the other, refined, even to the point of fussiness. Pearls feature regularly in Middle English writing, from lapidaries and romance to poems such as Pearl, in which the gem becomes an index of value itself. Pearls enable this rhetoric of preciousness because of their distinctive material composition. Grown inside a mollusk as the result of trauma, pearls acquire multiple coats of a calcium carbonate secretion called nacre that yields the gem’s classic play of rainbow tints. The outermost layers allow some light to pass through them, which reflects on the deeper layers, making the pearls faintly translucent. Surface and depth interact, giving the gem interior life. Poetic language similarly reverberates among multiple sounds and meanings through rhyme, puns, repetition, etc. Pearly diction also engages with figurative language to develop meanings occurring on several planes of representation. In an explicit analogy with human reproduction, natural histories and lapidaries explain the etiology of pearls as dew that drops from the sky into the mollusk’s opened shell. The origination theory invites explicit comparison with the Christian Incarnation. Human reproduction is also invoked to explain the formation of gems, acquiring what natural philosophers call mineral virtue (virtus mineralis). I close by considering the connection between the provenance of pearls and the native resources of Middle English poetry.