(b. Zonfingen, Switzerland, 26 June 1888; d. Zurich, Switzerland, 13 January 1953), crystallography, mineralogy, petrology, geology, chemistry.
Niggli’s father was a teacher and principal of the technical high school at Zofingen. Both his father and his Gymnasium teacher Fritz Mühlberg sparked his lifelong enthusiasm for the natural sciences and for geological-mineralogical problems in particular. As early as his high school years he participated in the mapping of his home canton; and at the age of nineteen he wrote his first scientific paper, “Die geologische Karte von Zofingen” (1913).
In the fall of 1907 Niggli enrolled in the Section for Natural Science Teachers at the Eidgenössiche Techsche Hochschule in Zurich. His early interest in both the descriptive and the analytic aspects of research prompted him to choose a petrologic topic for his M.S. thesis under Ulrich Grubenmann. In 1911 he received his teacher’s diploma and, after a brief stay in the department of physical chemistry of the Technical University at Karlsruhe, received his Ph.D. in 1912 at the University of Zurich. His thesis, which became famous, was entitled Die Chloritoidschiefer des nordöstlichen Gotthardmassivs. It showed the traits of Niggli’s style of research, the combination of a fundamentalist approach with a strong trend toward the integration of broad aspects.
Shortly after receiving his doctorate, Niggli qualified as a lecturer; and in 1913 he was at the Geophysical Laboratory of the Carnegie Institution in Washington, D.C., where he worked with Norman L. Bowen on phase diagrams of petrology, especially those with a volatile component. From the end of 1915 to 1918 he was a professor at Friedrich Rinne’s Institute at Leipzig; he then taught for two years at Tübingen. In 1920 Niggli succeeded Grubenmann as professor of mineralogy and petrography at the University of Zurich and the Swiss Federal Institute of Technology. He held these positions until his death, receiving but declining offers from well-known foreign universities.
Niggli’s influence is still felt in virtually all fields of applied and pure crystallography, mineralogy, and petrology. To those who did not know him Niggli appeared at times to be dry or even unfriendly; this was a result of his intense dedication to his work and his modest, simple, and direct way of dealing with people. To a majority of his students, co-workers, and friends he was by no means authoritative or despotic; he was warm and interested in their scientific problems and education and in their more personal affairs. His terms as rector of the Eidgenössische Technische Hochschule (1927–1931) and the University of Zurich (1940–1942) are proof of his talent for organization and his interest in public affairs. Nevertheless, the intensity of his scientific disputes, particularly over transformism, spilled over to affect personal relationships and the careers of two generations of Swiss geologists.
Niggli took a great and continuing interest in his teaching. During his thirty-two years at Zurich he constantly sought to improve all aspects of instruction in his field, in order to offer the students a well-rounded education. His courses were rather condensed and often hard to follow because of the wealth of material presented in a short time. The advanced student or co-worker could, however, gain much from taking the “same” course a second time, not only because of the density and breadth of material but also because Niggli hardly ever gave the same lecture in the same way or with the same content.
Although Niggli was mainly interested in theory, he devoted considerable time to the field and to the field training of his students. The excursions were always well prepared; and Niggli attempted to offer a balanced program covering igneous, metamorphic, sedimentary, and applied petrology.
Niggli’s significant accomplishments range from theoretical considerations of crystal lattices through many facets of petrology and geochemistry to that very practical problems of avalanche prevention through snow petrology and mineralogy. His crystallographic accomplishments were summarized by P. P. Ewald:
Crystallographers will remember him as the author of Geometrische Kristallographie des Diskontinuums (1919) in which lie transformed the theory of space groups from the mathematical skeleton left by Schoenflies (1891), E. S. Fedorov (1891), and Harold Hilton (1903), to a helpful friend and advisor of the modern crystallographer. This first of Niggli’s books testifies well to his aim of achieving convergence of previously separate fields. Once this was accomplished, he stopped; he never made an all-out attempt at structure determination, the details of which he may have felt likely to divert him from his main course. He kept, however, a profound interest in extending morphological methods to account for the inner structure of crystals. His two papers “Atombau und Kristallstruktur” (1921) contain a detailed survey of atomic and ionic volumes in the solid state throughout the periodic system and discuss the importance of similarity of volumes for the crystallographic properties of salts. His book Kristallographische und Strukturtheoretische Grundbegriffe(1928) is an attempt to arrive at a more refined classification of the translation lattices of structures and to connect to it the external morphology of the crystals. His papers “Topologische Strukturanalyse” and “Stereochemie der Kristallverbindungen” (1928–1933) serve as preliminary study for his book Grundlagen der Stereochemie, (1945), which, by its treatment of the internal morphology of crystals, is a counterpart to his textbook Spezielle Mineralogie (1924). Niggli’s urge for unifying, condensing and classifying knowledge so as to make it applicable to ever wider fields also stands out in papers on “Charaktertafeln” (1950–1951) in which a method is developed for symbolizing each space group so as to make any further reference to tables unnecessary.
Even in view of the infiltration of detailed wavemechanical bond theory into the realm of crystallography Niggli remained convinced of the lasting power of morphological methods. Morphology was the central theme of his interest and philosophy and has last large book Probleme der Naturwissenschaften erläutert am Begriffe der Mineralart (1949) is, in this sense, his testament [“Paul Niggli,” p. 240].
During the twenty years Niggli edited the Zeitschrift für Kristallographie, the journal acquired an international reputation. During these two first decades of X-ray analysis he strove to maintain a reasonable unified system of crystallographic terminology. It is also characteristic of his analytical mind that as early as 1919 Niggli recognized, in his Geometrische Kristallographie des Diskontinuums, the difference between “real” and “ideal” crystals, at that time speaking of the “pathology of crystals”.In 1934 Zeitschrift für Kristallographie published, at his urging, a double issue on ideal and real crystals. Niggli published over sixty papers on crystal structures and summarized this field in the two-volume Lehrbuch der Mineralogie und Kristallchemie (1941–1994); a third volume (dealing with crystal chemistry) was destroyed by fire in Berlin during the last months of World War II. These three volumes were actually the third edition of his Lehrbuch der Mineralogie (1920). Significantly, volume I contains the foundation of a statistical morphological science, the principles of which, largely original with Niggli, have only recently begun to find application. In his last years Niggli showed that even the wave-mechanical approach tea crystal physics required the assistance of morphological concepts, and he presented papers and lectures on the vibration symmetries and degrees of freedom of vibrations of atomic complexes.
In petrography and petrology Niggli also tended to be the integrating, unifying spirit. Almost a century of work had to be pulled together. It should be stressed that throughout his career Niggli used and emphasized the importance of physical chemistry and that phase diagrams formed an essential part of his courses on petrology and mineral deposits. But he did not mistake bare experimental results for proof of natural processes; rather, he was aware that experiments are bound to be oversimplifications, which are designed by man and may miss some essential factors present in natural processes. When experimental results did not match observations of nature, he suggested the possibility of misdirection or of missing parameters in the experiment.
Soon after his stay at the Geophysical Laboratory of the Carnegie Institution, Niggli recognized that his métier was integrating available experimental results instead of duplicating or adding to them. He accomplished this task in long, close teamwork with Bowen at the Geophysical Laboratory, A. Smits at Amsterdam, and especially with colleagues at the Eidgenössische Technische Hochsclaule and the University of Zurich.
Niggli applied the theory of phase equilibria for the first time to the role of volatile fractions in magmas, as also to problems of metamorphic petrology. The experimental criteria acquired during his work at the Geophysical Laboratory were soon applied to an understanding of the pneumatolytic and autohydrothermal alterations of the Eibenstock granite near Dresden, work done in cooperation with F. Rinne. The result was his first book, Die leichtflächtigen Bestandteile im Magma (1920), which received an award from the Fürstlich Jablonowitsche Gesellschaft in Leipzig and became a standard work. The 1937 book Das Magma und seine Produkte (mit besonderer Berücksichtigung der leichtffuchtigen Bestandteile) can be considered the second edition of the 1920 Work.
Niggli and his students undertook the gigantic task of petrographic classification and interpretation of the chemical analyses of the world’s rocks. The original CIPW-norm procedures proved to be inadequate for the project, so he modified them, creating “molecular values” which soon were used throughout the world and were known as Niggli values. These two fundamentally new principles inherent in these “values” calculated from the weight percentages of metal oxides are (1) conversion to atomic percentages instead of weight percentages, which blur the crystalchemical relationships, and (2) the immediate juxtaposition of the atomic abundance of the basic oxides (aluminium, iron, magnesium, manganese, calcium, sodium, and potassium) with that of silicon dioxide since most of these elements are contained in silicates. This allows the rapid calculation of the possible mineralogical composition of a rock.
Combined with variation diagrams and normative calculation schemes designed by Niggli and his coworkers (l922 1945), the new methods proved far superior to any others. Some of the basic ideas which he developed are (1) the principle of magmatic crystallization and tile influence of the volatile fraction; (2) the principle of gravitative crystallization differentiation in magmas: (3) the principle of petropgraphic geochemical provinces; and (4) the importance oft a calculation and a comparison of the normative and the modal composition of rock. His principal works on the, mineralogical composition of rocks were “Magma und Seine Produkte” (Naturwissenschafter, 9 , also published as a book in 1937); Gesteins und Mineralprovinzen (1923); “Die komplexe gravitative Kristallisationsdifferentiation” (Schweizerische mineralogische und petrographische Mitteilungen, 18 ); “Die Magmentypen,” written with A. H. Stutz (ibid., 16 ); and, with C. Burri, the two-volume Die jungen Eruptivgesteine des mediterranen Orogens (1945–1948). A late but important work was “Festeinschemismus und Magmenlehre.”
Niggli’s 1948 book Gesreine und Minerallagerstätten summarized his previous work. In it he developed petrologic science from the level of the crystal structure(including the role of tracer elements in petrology) to the mineral, the rock specimen as the mineral aggregate, the outcrop, the regional, and the global levels, in a synthesis of geochemical and geometric problems. The set of rock fabric patterns in this book illustrates his knowledge of petrographic-petrologic processes and fabric possibilities.
Niggli also applied his molecular values and norm calculations to metamorphic and sedimentary rocks to show that extreme transformist or relatively migrationist interpretations were oversimplifications. Extreme migrationist views were challenged about 1970–1973, when news global comparisons showed the average composition of sediments to be basaltic. rather than granitic. This revived a differentiation concept of anatexis, similar to that proposed by Niggli. The principles of metamorphic transformation were well known to him; but extensions of local processes try a regional scale were unacceptable to his critical mind.
Niggli insisted on the application of physicochemical principles, as is exemplified in all of his work on metamorphic rocks starting in 1913–1914 (some papers with. J. Johnston) and in the Gesteinsmetamorphose (1924), prepared with Grubenmann.
Niggli’s work is sometimes considered to be that of an “extreme orthodox magmatist.” On examination it is obvious that he was aware of the importance of exchange reactions in metamorphism. Nevertheless, before invoking a deus ex machina for the majority of igneous rocks, he insisted that the physicochemical aspects of the development of both igneous and metamorphic processes had to be understood. He was aware that his theory of magmatic processes and provinces was not the final answer to all problems of field petrology rind that additional work was needed. This is perhaps best expressed in a statement from his 1952 paper “Gesteinschemismus and Magmenlchre,” in which he explicitly states that there may be various ways of interpreting regional variations.
Niggli’s interest in sedimentary rocks led to original papers on clastic sediments, especially the morphological aspects of grains. His classification of shapes, developed with dal Vesco, is probably still the most widely uses) one. The general principles of Niggli’s petrology petrography, especially the close ties with his crystallographic interests, are summarized in volume 1 of Gesteine und Minerallagerstätten (1948), and he offered as complete a summary on sedimentary rocks in volume II. His papers on snow research, which had a profound impact in the held, also concern sedimentation, diagenesis, and metamorphism.
Niggli’ exerted a strong influence on applied petrology, especially through his work on rock weathering and other aspects of building, stone petroloy, most of it done with F.de Quervain, who headed the Geotechnische prüfstelle and the Geotechnische Kommission, both created at Niggli’ suggestion. Although never directly active in consulting work—he was too dedicated to fundamental science—Niggli nevertheless was in constant touch with applied fields of his science. He knew very well how often new “pure” aspects emerge from technological applications, and he also realized that most of his students had to prepare for work in applied fields. Also in this vein he promoted the publication of the geotechnical map of Switzerland and was active in the foundation of the Schweizerische Mineralogisehe und Petrographische Gesellschaft, of which he was president from 1928 to 1930.
Niggli wrote several papers and one booklet on ore deposits. Mere his main point of departure was the accumulation of metals during the gravitative crystallization differentiation and the accumulation of volatiles in later magmatic stages. His booklet Versuck einer natürlichen Klassifikation der im weiteren Sinne magmatischen Lagerstätten (1925) is a classic synopsis of magmatic ore deposits. In this work Niggli devoted less space to experimental problems and to direct observations of ore deposits, being more concerned to classify synopses of the published results and observations. This approach proved to be generally acceptable in crystallography, mineralogy, and petrology but rather negative with regard to ore deposits, the descriptive terminology of which was filled with preconceived genetic concepts. He did, however, recognize many physicochemical relationships within magmatic and hydrothermal ore deposits for the first time, especially the role of the volatile fraction in the accumulation of metals in a magma. His booklet was internationally quoted and used, especially the English translation.
I.Original Works. A summary of Niggli’s works can be found in R. L. Parker, “Memorial of Paul Niggli” (see below); a complete list of all publications is given by J. Marquard and I. Schroeter, in Schweizerische mineralogische und petrographische Mitteilungen,33 (1953), 9–20.
Niggli’s major works include Die Chloritoidschiefer des nordöstlichen Gotthardmassivs Kristallographie des Diskontinuums (Peipzig, 1918–1919); Lehrbuch der Mineralogie (Berlin, 1924–1926), 3rd ed., entitled Lehrbuch der Minerlogie und Kristallchemie, 3vols. (Berlin, 1941–1944), vol. III destroyed by fire; “Das Magma und seine Produkte,” in Naturwissenschaften,9 (1921), 463–471; Gesteins-und Mineralprovinzen (Berlin, 1923), written with P. I. Beger; Die Gesteinsmetamorphose (Berlin, 1924), written with U. Grubenmann; Versuch einer naturlichen Lagerstatten (Halle, 1925), trans. by Thomas Murby as Ore Desposits of Magmatis Origin. Their Genesis and Natural Classification (London, 1929); Tabellen zur allgemeine und speziellen Mineralogie(Berlin, 1927); Kristallographische und strukturtheoretische Grundbegriffe, which id Handbuch der Experimentalphysik,VII, pt. 1 (Leipzig, 1928); “Chemismus Schweizerscher Gesteine,” which is Beitrage zur Geologischen Karte der Schweiz, Geotechnische Reihe, 8, no. 14 (1930), wtitten with F. De Quervain and R. U. Wintehalter; Geotechnische Karte der Schweiz 1:200 000, 4 sheets (Bern, 1934–1938), Prepared with F. de Quervain, M. Gschwind, and R. U. Winterhalter; Internationale Tabellen zur Bestimming von Kristallstruktuten (Berlin, 1935), written with E. Brandenberger; and “Die Magmentypen,” in Schweizerishe mineralogische und petrographische Mitteilungen,16 (1936), 335–399, written with A. H. Stutz.
Also see Das Magma und seine Produkte (mit besonderer Berücksichtigung der leichtflüchtigen Bestandteile), (Leipzig, 1937), which is the 2nd ed. of Die leichtflüchtigen Bestandteile im Magma(Leipaig, 1920); “Die komplexe gravitative Kristallisationsdifferentiation,” in Schweizerische mineralogische und petrographische Mitteilungen,18 (1938), 610–664; La loi des phases en Schweizeralpen, 2 vols. (Basel, 1940), written with J. Koenigsberger and R. L. Parker; Grunglagen der Stereochemie (Basel, 1945); Die jungen Eruptivgestenis des mediterranen Orogens, 2 vols. (Zurich, 1945–1948), written with C. Burri; “Krystallogis von J. H. Hottinger (1698),” in Veröffentlichungen der Schweizerischen Gesellschaft für Gescgichte der Medizin und der Naturwissenschaften, no. 14 (1946); Gesteine und Mindeallagerstatten, 2 vols. (Basel, 1948–1952), written with E. Niggli; Probleme der Naturwissenschaften erautert am Begriff der Mineralart (Basel, 1949); “Gesteinschemismus und Magmenlehre,” in Geologishe Rundschau,39 (1951), 8–32; and International Tables for X-ray Crystallography (Birmingham, 1952), written with E. Brandenberger.
II. Secondary Literature. See E. Brandenberger, “Pal Niggli (1888–1953). Seine Verdienste um die Lehre des festen Körpers,” in Zeitschrift für angewandte Mathematik und Physik,4 (1953), 415–418; P. P. Ewald, “Paul Niggli,” in Acta crystallographica,6 (Mar. 1953), 225–226; P. Karrer and E. Brandenberger, Prof. Dr. Paul Niggli. Ansprachen zu seinem Gedenken (Zurich, 1953); F. Laves, “ Paul Niggli,” in Experientia,9 (1953), 197–202; F. Laves and A. Niggli, “In Memoriam: Paul Niggli’s Crustallographic Oeuver,” in Zeitschrift für Keistallograpjie und Mineralogie,120 (1964), 212–215; H. O’Daniel, K. H. Scheumann, and H. Schneiderhöhn, “Paul Niggli,” in Neues Jahrbuch für Mineralogie (1953), 51–67; R. L. Parker, “Memorial of Paul Niggli,” in American Mineralogist,39 (1954), 280–283; F. de Quervain, “Prof. Dr. Paul Niggli,” in Schweizerishe mineralogische und petrographische Mitteilingen,33 (1953), 1–20; K. H. Scheumann, “Paul niggli und sein Werk,” in Geologie,2 (1953), 124–130; and A. Streckeisen, “Paul Niggle,” in Mitteilungen der Naturforschenden Gesellschaft in Bern, n.s. 11 (1954), 109–113.