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Reference Samples in Geology and Geochemistry Reference Samples in Geology And Geochemistry U.S. GEOLOGICAL SURVEY BULLETIN 1582 I • .. I· r 1 .1.. ' ~~~- . ' -: I• p !I - I .. 1· ..._. I' ,.,• Reference Samples in Geology And Geochemistry By F. J. FLANAGAN The report discusses some history of analytical problems that resulted in early standards. Geologic samples of economic interest and general information are discussed by country of origin, whereas geochemical samples are mentioned by samples types and by their intended use. Numerous topics and problems for reference samples and their data are discussed. U.S. GEOlOGICAl SURVEY BUllETIN 1582 DEPARTMENT OF THE INTERIOR DONALD PAUL HODEL, Secretary U.S. GEOLOGICAL SURVEY Dallas L. Peck, Director UNITED STATES GOVERNMENT PRINTING OFFICE: 1986 For sale by the Distribution Branch, U.S. Geological Survey, 604 South Pickett Street, Alexandria, VA 22304 Library of Congress Cataloging-in-Publication Data Flanagan, F.j. (Francis James), 1915- Reference samples in geology and geochemistry. (U.S. Geological Survey bulletin ; 1582) Bibliography: p. 56 Supt. of Docs. no.: 119.3:1582 1. Rocks-Composition. 2. Mineralogy, Determina­ tive. 3. Sediments (Geology)-Composition. I. Title. II. Series. QE75.B9 no. 1582 [QE438] 557.3 s 85-600274 [552'.06] CONTENTS Abstract 1 Introduction and historical review 1 Analysis of natural materials and mixtures 2 Zinc ores 4 Products made from ores 4 1901 and precursors of geochemical standards 5 Uniformity in rock analysis 6 Plant pest control regulations 6 Sources of information on reference samples 7 Samples for geology and geochemistry 8 Artificial samples 8 Solutions 8 Solid chemicals 8 Mixtures of natural materials 8 Glass samples for major and minor elements 8 Glass samples for trace elements 9 Dust and particulate samples 9 Gelatin samples 10 Implantation, dip, and urea samples 10 Resin and polymer samples 10 Silica gel samples 10 Sludge ash sample 10 Waste incineration ash 11 General synthetic samples 11 Natural samples of economic interest 11 United States 11 Great Britain 11 France 12 Germany 12 Canada 12 South Africa 12 CMEA Countries 12 Czechoslovakia 12 German Democratic Republic 13 Poland 13 U.S.S.R. 13 Austria 14 BCR (Community Bureau of Reference, Brussels) 14 Brazil 15 Japan 15 People's Republic of China 15 Scandinavia 16 Natural samples of geologic interest 16 Geological and geochemical samples 16 Geochemical exploration samples 17 Archaeology 17 Bauxite 17 Clays and clay minerals 17 Coals, coal ash, and cokes 18 Counting standards 18 Laterites 18 Meteorites 18 Minerals 19 General 19 Contents Ill Samples for geology and geochemistry-Continued Natural samples of geologic interest-Continued Minerals-Continued For microprobe 19 For age determinations 19 Phosphates 19 Sediments 19 Bay (Estuarine) 19 Canal (River) 20 Lake 20 Marine 20 Pond 20 River (Radioactivity) 20 Soils 20 General 20 Low-level radioactivity 20 "Natural matrix" vs. spiked samples for radioactivity 20 Stable isotope 21 Geobotanical samples 22 Topics and problems for reference samples and their data 23 Reasons for reference samples 23 Amount of a rock reference sample 24 Reference samples vs. in-house standards 25 Comminution and grindability 25 Homogeneity, sampling errors, and the sample for analysis 25 Small samples-Precautions and preparation 28 Excess grinding and the FeO contents of rocks 30 Large samples-Precautions and preparation 30 Sieving 32 Contamination by steel 33 Homogeneity of reference samples 33 Outliers 35 Estimation of best values 36 Certification factor 37 Nomenclature for reference samples 37 Are "best values" best? 38 Confidence limits for a single datum 39 Comparisons of data 40 The analyst and the producer 41 Reference samples identified through 1984 41 References cited 56 FIGURES 0 1. Plot of the free iron (Fe ) contents of some reference samples determined by two chemical methods 33 2. Confidence limits for a calibration line 39 3. Confidence rectangles for assigning points x ,y to rock fields 40 TABLES 1. K20 in commercial fertilizers, determined by the chloroplatinate method 2 2. K20 in commercial fertilizers, determined by variations of the chloroplatinate method 3 3. K20 determined by the Association-recommended method 3 4. Summary of methods relating sampling, errors, and particle size 28 5. Reference samples 42 6. Suppliers of reference samples 55 IV Contents Reference Samples in Geology and Geochemistry By F. j. Flanagan Abstract Because of the large increase in the number of reference The use of geologic reference samples may have started samples of all types, a revised table listing samples that may be in the last quarter of the 19th century after analysts in England, useful in geochemistry is included. It is not known if the sam­ Germany, and the United States deplored the large variation in ples, other than those of the U.S. Geological Survey, were data obtained by different analysts for the same constitutent in collected in conformance with provisions of the Plant Pest the same sample. Early samples involved in cooperative analy­ Control Regulations of the U.S; Department of Agriculture, or sis, also known as "round robins," were mainly industrial or of similar organizations in other nations. agricultural materials of economic value, or products derived from them. Data from some round robins were so diverse that INTRODUCTION AND HISTORICAL REVIEW "uniformity in analysis" was a part of early committee names. The first two geologic samples of the National Bureau of Stand­ Reference samples in geology and geochemistry are ards were analyzed cooperatively. now used so widely that many of us take for granted their Samples for geology and geochemistry are classified as availability. Yet little more than three decades ago, before artificial samples or as natural materials of either economic or the results of a cooperative study on G-1 and W -1 were geochemical interest...:_the latter distinction not always possi­ published (Fairbairn and others, 1951), no reference sam­ ble. Artificial samples have been prepared in several substrates, and samples in other substrates may be limited only by the ples of silicate rocks were available. The rocks in the coop­ ingenuity of the analyst. erative study were generally known as granite G-1 and The principal suppliers of samples of economic interest diabase W -1 by those concerned both with the study and are discussed, by country, to show the range of samples pre­ with the distribution of the samples, but the two samples pared by organizations. Natural samples of geochemical inter­ were soon promoted by users to the status of "standards." est are mentioned by sample type. Because of their intended Reasons for this promotion may become evident if we con­ use, some geochemical samples are restricted to analysts using sider why and when samples of geologic materials were first specific techniques. prepared and used. Methods used for and precautions to be observed while preparing large or small rock samples are discussed. Excess A search of the chemical and geological literature to grinding of small rock samples reduces the amount of FeO determine when geologic reference samples were frrst used found in a rock analysis. Unavoidable contamin.ation occurs highlights the pertinence of the following remark by Pirsson when processing rocks in steel. Tungsten carbide, and some (1918, p. 250) about the rise of petrology: "The beginnings mechanical equipment, should be avoided. A review of the of a particular branch of science are generally obscure and allied subjects of homogeneity of a sample, sampling errors, rooted so imperceptibly in the foundations on which it rests and size of the sample grains shows that we have reinvented that it is difficult to point to any particular place in its the wheel since 1885. development and say that this is the start." Standard samples Methods used to (1) test the homogeneity of samples, went through an extended period of incubation, and the (2) eliminate outliers which some scientists reject repeatedly despite warnings of statisticians, and (3) estimate best values greatest hindrance to determining when geologic reference when the method for estimating should be part of the program samples were frrst used has been the several changes in for a sample are discussed. Calibration lines may be used to nomenclature since the last century. determine if "best values" in a series of several samples are The trend in the last decade has been to refer to such really "best" and to furnish confidence limits for a single da­ materials as either reference samples, standard reference tum. materials, or certified reference materials, with CRM as the The agreement of data by an analyst for a reference sam­ accepted abbreviation for the latter. The term "standard ple with data preferred by an issuing organization is usually sample" was used perhaps universally during the preceding described by one of several adjectives, a subjective procedure. half century. Prior to that, Hillebrand (1909), shortly after A variation of a x2 method may be used if a producer specifies the exact number of data for the cooperative analytical pro­ he transferred from the U.S. Geological Survey to the Na­ gram to be furnished by each analyst and then calculates the tional Bureau of Standards, published the short note "The population estimates of the mean and standard deviation for an Bureau of Standards' Analyzed Samples," but in the follow­ element in a sample. ing year [National] Bureau of Standards (1910) Circular 25 Introduction and Historical Review had the
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