De Re Metallica
His most famous work, the De re metallica libri xii long remained a standard work, and marks its author as one of the most accomplished chemists of his time. It was published the year after his death, in 1556, though apparently finished in 1550, since the dedication to the elector and his brother is dated 1550. The delay in publication is thought to be due to the time necessary to complete the book's many woodcuts. The work is a complete and systematic treatise on mining and extractive metallurgy, illustrated with many fine and interesting woodcuts which illustrate every conceivable process to extract ores from the ground and metal from the ore, and more besides.
He acknowledged his debt to ancient authors, such as Pliny the Elder and Theophrastus. Until that time, Pliny's work Historia Naturalis was the main source of information on metals and mining techniques, and Agricola made numerous references to the Roman encyclopedia.
Agricola described and illustrated how ore veins occur in and on the ground, making the work an early contribution to the developing science of geology. He described prospecting for ore veins and surveying in great detail, as well as washing the ores to collect the heavier valuable minerals, such as gold and tin.
The work is also interesting for showing the many water mills used in mining, such as the machine for lifting men and material into and out of a mine shaft. Water mills found innumerable applications, especially in crushing ores to release the fine particles of gold and other heavy minerals, as well as working giant bellows to force air into the confined spaces of underground workings.
He described many mining methods which are now redundant, such as fire-setting, which involved building fires against hard rock faces. The hot rock was quenched with water, and the thermal shock weakened it enough for easy removal. It was very dangerous when used in underground galleries for the toxic gases given off by fires, and was made obsolete by explosives.
The work contains, in an appendix, the German equivalents for the technical terms used in the Latin text. Modern words that derive from the work include fluorspar (from which was later named fluorine) and bismuth. In another example, believing the black rock of the Schloßberg at Stolpen to be the same as Pliny the Elder's basalt, Agricola applied this name to it, and thus originated a petrological term which has been permanently incorporated in the vocabulary of science.
De re metallica is considered a classic document of Renaissance metallurgy, unsurpassed for two centuries. In 1912, the Mining Magazine (London) published an English translation. The translation was made by Herbert Hoover, then an American mining engineer (better known to history for his later term as a President of the United States), and his wife Lou Henry Hoover.
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