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Open-File Report 2003-78

User's Guide to RockJock -- A Program for Determining Quantitative Mineralogy from Powder X-Ray Diffraction Data

By D.D. Eberl

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RockJock is a computer program that determines quantitative mineralogy in powdered samples by comparing the integrated X-ray diffraction (XRD) intensities of individual minerals in complex mixtures to the intensities of an internal standard. Analysis without an internal standard (standardless analysis) also is an option. This manual discusses how to prepare and X-ray samples and mineral standards for these types of analyses and describes the operation of the program. Carefully weighed samples containing an internal standard (zincite) are ground in a McCrone mill. Randomly oriented preparations then are X-rayed, and the X-ray data are entered into the RockJock program. Minerals likely to be present in the sample are chosen from a list of standards, and the calculation is begun. The program then automatically fits the sum of stored XRD patterns of pure standard minerals (the calculated pattern) to the measured pattern by varying the fraction of each mineral standard pattern, using the Solver function in Microsoft Excel to minimize a degree of fit parameter between the calculated and measured pattern. The calculation analyzes the pattern (usually 20 to 65 degrees two-theta) to find integrated intensities for the minerals. Integrated intensities for each mineral then are determined from the proportion of each mineral standard pattern required to give the best fit. These integrated intensities then are compared to the integrated intensity of the internal standard, and the weight percentages of the minerals are calculated. The results are presented as a list of minerals with their corresponding weight percent. To some extent, the quality of the analysis can be checked because each mineral is analyzed independently, and, therefore, the sum of the analysis should approach 100 percent. Also, the method has been shown to give good results with artificial mixtures. The program is easy to use, but does require an understanding of mineralogy, of X-ray diffraction practice, and an elementary knowledge of the Excel program.

First posted March 2009

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Suggested citation:

Eberl, D.D., 2003, User's guide to RockJock -- A program for determining quantitative mineralogy from powder X-ray diffraction data: U.S. Geological Survey Open-File Report 2003-78, 47 p.



Contents

Abstract

Summary of Instructions for a Quick Start

Introduction

Computer Requirements and Disclaimer

How To Obtain RockJock

Installation of RockJock

Acknowledgments

Running RockJock

Using the Automatick Mode

Using the Manual Mode

Sample Preparation and Analysis

Entering New Standards into the Program

Measurement Accuracy

Useful Tips

References

Appendix 1: Input Sheet Inputs and Outputs

Appendix 2: Shifter Sheet Inputs and Outputs

Appendix 3: Full Pattern Sheet Inputs and Outputs

Appendix 4: Result Sheet Inputs and Outputs

Appendix 5: Standards Sheet Inputs

Appendix 6: Auto XRD Sheet Inputs

Appendix 7: Auto Results Sheet Outputs

Appendix 8: Auto Graph Sheet Inputs

Appendix 9: Resources for Quantitative Mineral Analysis

Appendix 10: Analysis of Reynolds Cup Samples


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