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Mineral Standards for Quantitative X‐Ray Diffraction Analysis of Soil Clays: I. Abridgement of Component Percentages Based on Weathering Sequence
Author(s) -
Willis A. L.,
Pennington R. P.,
Jackson M. L.
Publication year - 1948
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1948.036159950012000c0090x
Subject(s) - library science , weathering , geology , computer science , geochemistry
E primary step in interpretation of the diffrac1 tion pattern is measurement of diffraction intensity at characteristic angles. Crystal lattice factors of the mineral, in general, control the diffraction intensities. Thus, each type of mineral, such as quartz, illite, or montmorillonite, diffracts X-rays at characteristic angles which are unique in intensity depending on lattice factors within the type of crystal involved. For example, pure quartz diffracts at a Bragg angle corresponding to a 3.35 A. spacing, with an intensity far in excess of that of the 4.45 A. spacing of illite or montmorillonite. Quantitative interpretation of diffraction patterns is begun with an appraisal of the diffraction intensity of the standard mineral and that of the same component in the test sample, computed relatively, as a ratio or percentage. In practice, the relative intensity at a given diffraction angle of the test sample in ratio to the standard mineral sample is measured chiefly through one of three methods as follows: