Georgius Agricola (1494-1555)

I have omitted all those things which I have not myself seen, or have not read or heard of from persons upon whom I can rely. That which I have neither seen, nor carefully considered after reading or hearing of, I have not written about. The same rule must be understood with regard to all my instruction, whether I enjoin things which ought to be done, or describe things which are usual, or condemn things which are done.

Agricola, Preface to De Re Metallica, 1556

Georg Bauer, better known by the Latin version of his name Georgius Agricola, is considered the founder of geology as a discipline. His work paved the way for further systematic study of the Earth and of its rocks, minerals, and fossils. He made fundamental contributions to mining geology and metallurgy, mineralogy, structural geology, and paleontology.

Born in Glauchau, in the province of Saxony in what is now Germany, Agricola studied classics at Leipzig University, taught Latin and Greek for a few years, and then in 1522 began to study medicine, first at Leipzig and then at Bologna and Padua in Italy. He took his degree in 1526 and became a practicing doctor; however, he never seems to have been terribly enthusiastic about his profession, devoting most of his energy to studies of mining and geology. He began practicing medicine at Joachimsthal in 1527. Joachimsthal was an important mining center of the time, in particular for silver mining. Agricola's geological writings reflect an immense amount of study and first-hand observation, not just of rocks and minerals, but of every aspect of mining technology and practice of the time. Agricola moved in 1536 to the city of Chemnitz, also an important center of the mining industry, and was elected Burgomaster there in 1546. He not only continued his medical practice and his geological studies there, but was appointed to several public and diplomatic posts by Duke Maurice of Saxony, to whom he dedicated his book De Natura Fossilium. He died in 1555, one year before the posthumous publication of De Re Metallica, his greatest work.

De Re Metallica, literally translated, means "On the Nature of Metals," but the word metal had a wider meaning at the time, and meant any mineral. In this book, which remained the standard text on mining for two centuries, Agricola reviewed everything then known about mining, including equipment and machinery, means of finding ores -- he rejected the use of divining-rods and other such magical means -- methods of surveying and digging, assaying ores, smelting, mine administration, and even occupational diseases of miners. The book also contains descriptions of ores and of strata. His book was profusely illustrated; one illustration, showing mine shafts, is shown at left (click on the small image to view an enlargement). Agricola noted that rocks were laid down in definite layers, or strata, and that these layers occurred in a consistent order and could be traced over a wide area. This observation of Agricola's was one of the first contributions to stratigraphic geology, and one that would become important in understanding the arrangement and origins of the rocks of the Earth.

Agricola also wrote the first book on physical geology, De Ortu et Causis Subterraneorum (1546), notable for its descriptions of wind and water as powerful geological forces, and for its explanation of earthquakes and volcanic eruptions as produced by subterranean vapors and gases heated by the Earth's internal heat. However, his greatest contribution to paleontology was his book De Natura Fossilium (On the Nature of Fossils), also published in 1546. This book is not restricted to what we call fossils today: the Latin word fossilis meant anything dug out of the ground, and Agricola's book included descriptions of all kinds of minerals, gemstones, and even gallstones, in addition to what we would call fossils now. Agricola's work summed up what the ancient Greek and Roman authors had written about minerals, and included a list of a hundred ancient authors whose works Agricola had consulted -- but Agricola was not afraid to contradict the ancients' opinions if they did not fit with his own experience. His work represented a major advance over previous writings on rocks and minerals in that it classified them, not alphabetically or by their supposed mystical powers, but by simple physical properties: "Thus minerals have differences which we observe by color, taste, odor, place of origin, natural strength and weakness, shape, form, and size." Agricola gave standardized names to various minerals, and not only recorded their appearance but the localities where they could be found. He also noted how the same fossils might have different colors and appearances in different places. Although Agricola's work included no pictures, his descriptions of fossils are often instantly recognizable:

"Lapis judaicus. . . usually occurs in the form of symmetrical acorns. Prominent lines run from the blunt to the pointed end and these are so regular they appear to have been made in a lathe and resemble the striae on a shell. The people who call this mineral pyren liken these lines to the bones of a fish that extend from the back down to the belly. . . When split open it is light inside and glistens like marble and in some cases the outside also has a high luster."

"Certain rocks, when split open, are found to contain shells; for example, the conchites beds of Megara and the rocks of France. . . Ostracites is a stone that takes its name from ostreum [oyster] which it resembles. There are two species, the larger found in the moat on the north side of Hildesheim. . . The smaller species is found not far from Hanover on a cliff near the village of Linda in an unctuous light green earth. . . . It forms in strata that are conspicuous. When tapped with the finger it has the sound of a jug."

Agricola noted the resemblance of many of his "fossils" to living organisms, but rarely stated that any of his fossils actually did represent once-living organisms. The question of whether fossils did represent once-living organisms was still debated in Agricola's time, and was not finally resolved until the early 18th century, after the work of scientists like John Ray and Robert Hooke. While Agricola rejected some of the popular superstitions of his time, he listed the medicinal and even magical uses to which rocks, minerals and fossils were put: powdered lapis judaicus (the blastoid echinoderm Pentremites) was prescribed for kidney stones, while ostreites (fossil oyster shell), moistened with water, "reduces inflammation of the breasts, heals ulcers and is poisonous to crawling insects." Nevertheless, Agricola's work was important for the development of geology and paleontology as scientific disciplines, for its classification by physical properties and localities, its simple standardized naming system, its careful summarization of previous work, and above all its use of observation and personal experience.

There is another Agricola page maintained at the University of Bologna, Italy, with more detailed information about Agricola's life and work (mostly in Italian at this time). More pictures from De Re Metallica are also available. And the city of Chemnitz (known as Karl-Marx-Stadt from 1953 to 1990) recently celebrated Agricola's 500th birthday and presented some information (in German) on his life.