This paper investigates the early history of the pigment known as ultramarine blue and its use, from its first appearance in Chinese cave paintings (2nd–3rd century CE) to the famous description of the technique known as per pastillum found in Cennino Cennini’s Libro dell’Arte (14th–15th century). My discussion will be based on archaeological findings as well as written sources in order to show how the knowledge linked to the production of this highly valued pigment from the semi-precious stone lapis lazuli travelled throughout countries and cultures. I shall focus in particular on Medieval Arabo-Islamic sources (Jābir ibn Ḥayyān, Al-Rāzī, al-Bīrūnī, Al-Tīfāshī) describing lapis lazuli and its features; some significant mentions of lapis lazuli in manuscript fragments from the Cairo Genizah; and descriptions of its preparation in Persian bookmaking treatises (Ibn Bādīs, Abū-’l-Qāsim ‘Abdallāh b. ‘Alī).