De re metallica (Latin for On the Nature of Metals [Minerals]) is a book in Latin cataloguing the state of the art of mining, refining, and smelting metals, published a year posthumously in 1556 due to a delay in preparing woodcuts for the text. The author was Georg Bauer, whose pen name was the Latinized Georgius Agricola ("Bauer" and "Agricola" being respectively the German and Latin words for "farmer"). The book remained the authoritative text on mining for 180 years after its publication. It was also an important chemistry text for the period and is significant in the history of chemistry.
Mining was typically left to professionals, craftsmen and experts who were not eager to share the experiential knowledge they had accumulated over centuries; this knowledge was passed down orally within a small group of technicians and mining overseers. In the Middle Ages, these people held the same leading role as the master builders of the great cathedrals, or were perhaps like alchemists; a small, cosmopolitan elite within which knowledge was guarded from the outside world. Only a few writers found it worth the effort to write about mining, and only in the Renaissance did this begin to change. With improved transport and the invention of the printing press, knowledge spread much faster than before. In 1500, the first printed book dedicated to mining engineering, called the Nützlich Bergbüchleyn ("The Useful Little Mining Book") was published by Ulrich Rülein von Calw. The most important works in this genre, however, were the twelve books of De Re Metallica.
