The time between 1640, when Álvaro Alonso Barba published his Arte de los metales (Art of Metals), and 1761, when Francisco Xavier de Gamboa published his Comentarios a las ordenanzas de minas (Commentaries on Mining Ordinances), was a transitional period in which scientific mining and metallurgical knowledge in Spanish America became operative and practical and replaced the long-standing Spanish (and European) medieval tradition of the theory of minerals and metals. Barba was the last representative of this tradition, inheriting the complex world of the classical writers, the medieval alchemists, the first news from the new American...