Inside Kirwan's Mineralogy

B"efore 1780, Richard Kirwan explained in the Preface to his two-volume Elements of Mineralogy,1 his subject could scarcely be deemed a science because, despite the efforts of men such as Carolus Linneaeus, its nomenclature was in chaotic disarray. The same substance "from some slight variation of appearance was often denoted by different names, and different substances by the same name; its descriptive language, was, for the most part, arbitrary, vague, and ambiguous, each author using that which seemed to him best to answer this purpose."2 kirwan's mineralogy title pageIn 1794 the German geologist Abraham Gottlob Werner (1750-1817), employing chemical analysis, reduced the descriptive language of mineralogy to "as much precision as it was capable of receiving."3

In the ensuing decade, marked by the publication of the first edition of Kirwan's Mineralogy in 1784, the subject "for the first time assumed its rank among the sciences, its simplest elements having been for the most part discovered,...its leading distinctions ascertained, and the great art of resolving the most complex into the simplest substances...in a manner created." By the time of the second edition, in 1794, Kirwan could claim that "the gross indications of the unassisted senses, freed from their attendant fallacies," had been restored to scientific procedure, while "the great art of analysis, extended far beyond its former limits, now nearly reaches the precision of an algebraic formula."

T"he following excerpt from Kirwan's manual will serve to show why, although Lewis and Clark had the book at hand throughout the expedition, they often made mistakes in identifying "flint," as well as many other rocks and minerals. The figures in this excerpt refer to scales of various qualities, such as hardness, reflecting the analytical precision that Kirwan helped to establish for his time. Many of the standards he applied are no longer valid.

Flint. Feuer Stein [fire stone] of the Germans. – Commonly of a yellowish, or bluish grey colour; the latter, however, often passes into the grayish black, and the former into ochre yellow, or brown. Several of these often meet in the same specimen, either in veins, stripes, clouds, or dots.

Amorphous, interspersed in other stones, or in nodules, or rounded lumps, often perforated, very rarely crystallized, in double triangular pyramids; often also forming the substance of petrification, particularly of echinites. Its surface generally uneven and wrinkled, either smooth or rough, often covered with a rind, either calcarous or argillaceous. Its external lustre, 0 or 1. Internal, 1. Transparency, 2.1, sometimes nearly 3. Fracture conchoidal, seldom imperfectly. Fragments, 3.

Hardness, from 10 to 11. Specific gravity, from 2.58 to 2.63.

Heated, it decrepitates, whitens, becomes brittle, and opaque, is unfusible at 168°, and is barely softened by pure air; the usual fluxes affect it as they do quartz.

The impressions of marine shells, and even of leaves, are frequently found in flints, which leaves no doubt of their having been produced in the moist way, and even that some are of modern formation.

According to Mr. Weigleb's analysis they contain about 0.80 silex, 0.18 argill, and 0.02 calx.

Its transitions are into quartz, calcedony, carnelian, and hornstone.

Flint had been mined to make cutting tools since at least the Lower Palaeolithic Period, about 700,000 years ago. In the early 16th century A.D. it (as well as iron pyrite) began to be used to ignite powder in the new wheel lock musket, which was superseded a century later by the flintlock, which was the technology used in most of the firearms the Corps of Discovery carried. It remained the preferred ignition source for firearms until the percussion cap was introduced around the middle of the 19th century.4 Throughout the period, flint was mined for flintlocks in France, Germany, and Poland. In the 1780s the best flints came from the chalk cliffs at Brandon, England.

At the time of the Lewis and Clark expedition, common usage still made the term flint the primary one, allowing Noah Webster, in his Compendious Dictionary of the English Language (1806) to define chert as "a kind of flint." Even now, flint is considered a separate species by many rock-hounds5 as well as by black-powder gun enthusiastists. The science of geology, however, has since reversed the nomenclature, identifying flint as simply a black or very dark brown variety of chert. Microscopic examination reveals that all chert is a felted mass of extremely small quartz grains. Its appearance under the microscope suggests a felted mass of hair. Regardless of its color, chert has a generally waxy appearance, and breaks like glass along smoothly curving and slick surfaces to make chips with sharp edges. Blades newly chipped from chert are extremely sharp, though they soon dull as fine chips flake off the keen edge during use.

Kirwan's book was meant for the serious scientist of the day. It contained a bewildering array of technical terms that Lewis and Clark had insufficient knowledge to employ. It gave details of laboratory tests that they were not equipped to apply, and would not have had time to undertake. A typical analysis would have required as many as 60 steps, and could have taken more than two days. The equipment would have included a blowpipe, a Bunsen burner or alcohol lamp, a pyrometer, test tubes, and a balance or scale for determining specific gravity (they had one or more scales, but there is no evidence they ever tried to determine specific gravity); the chemicals required for mineral analysis would have included hydrochloric, nitric, and sulphuric acids, plus several dry reagents. Moreover, without suitable illustrations, especially colored ones, even the captains' "unassisted senses" were at a disadvantage in the field.6

O"f the 67 or 68 mineralogical specimens – "earths, salts, and minerals," plus a fossil or two – that Lewis sent back from Fort Mandan in April of 1805, he identified only one, "found at the white Chalk Bluffs 1804," as flint. Adam Seybert,7 a member of the American Philosophical Society, examined the collection sometime after it reached the East and added some annotations to Lewis's list, identifying two specimens as agatized flint that Lewis had merely called "pebbles," but making no comment on the one Lewis labeled flint. Sometime after the Academy of Natural Sciences was founded in 1812, the specimens were moved there, and all were integrated into the Academy's main collection, without attribution. Only one, now held in the Lewis and Clark Herbarium, still bears Lewis's own label: "Petrified Jawbone of a fish or some other animal . . . by Searjant Gass."


1. First edition, one volume, Dublin, 1784; second (enlarged) edition, two volumes, Dublin, 1794. Roger Wendlick, of the Watzek Library at Lewis and Clark College in Portland, Oregon, believes that Lewis carried the second edition on the expedition, from which the following quotations have been taken (1:v, 264-265). There is some evidence in the journals that Clark, at least, read Kirwan's section on "Arenaceous Quartz or Sand." Stephen Dow Beckham, The Literature of the Lewis and Clark Expedition: A Bibliography and Essays (Portland, Oregon: Lewis and Clark College, 2003), 30-31. Kirwan included a section on "Geological Observations" containing his definition of mountains and their origins, as well as a formula for determining their height, plus discussions of fossils and volcanoes. All of this may have been interesting to the captains--it is certainly illuminating, historically, to us--but there appears to be no trace of its influence upon either explorer during their trips through the Rockies or the Cascades.

2. Ibid., 1:x-xi.

3. Ibid., 1:xi. Werner was the founder and leading exponent of the theory of Neptunism, according to which rocks, the essential substance of dry land, were held to have precipitated in distinct, orderly layers from a primordial global ocean. Basing his theory solely on observations made in his family's iron mines in Saxony, and on the assumption they were the same for the whole world, he developed the science he called geognosy, which he taught for 40 years, beginning in 1775, at the School of Mining in Freiberg, Germany. He rejected the idea of a molten core to the Earth, explaining volcanoes as the result of the spontaneous combustion of underground coal beds. Although he published nothing of any significance, Werner's brilliant lectures inspired some of the foremost geologists of the next generation, including several Americans. The opposing theory was that of the Vulcanists, who held that rocks were igneous materials. John C. Greene, American Science in the Age of Jefferson (Ames: Iowa State University Press, 1984), 220.

4. The first successful experiments with the percussive ignition of potassium chlorate and fulminate of mercury, were made in 1805 by a Scottish contemporary of Lewis and Clark, Alexander Forsyth (1769-1843), and patented in 1807. In 1842 the percussion lock became the basis for modern firearm engineering.

5. Chris Pellant, Smithsonian Handbooks: Rocks and Minerals, 2nd American edition (New York: DK, 2002), 246.

6. Roger Wendlick has found a convincing coincidence between Kirwan's manual and Clark's discussion of the "Strater of white earth" he observed near the top of Tillamook Head on 7 January 1806. There is no other evidence in the journals that the captains actually used Kirwan's Mineralogy. The Literature of the Lewis and Clark Expedition: A Bibliography and Essays; Essays by Stephen Dow Beckham, Bibliography by Doug Erickson, Jeremy Skinner, and Paul Merchant (Portland: Lewis and Clark College, 2002), 22.

7. Adam Seybert (1773-1825), was a native of Philadelphia. He graduated from medical school at the University of Pennsylvania in 1793, and continued his education in Europe at Edinburgh, Gˆttingen and Paris. After returning to America he devoted his attention to chemistry and mineralogy, and was elected to membership in the American Philosophical Society in 1797. He served as a Representative to Congress from Pennsylvania for three terms. His son, Henry (1802-1883), attended the …coles des Mines in Paris, and became well known for his analyses of minerals in the U.S. Greene, American Science, 223.