Derivation of Mineral formulas from the Chemical Analysis of Minerals by Computer
Abstract
The procedure for deriving formula and atomic ratios from the analyses of feldspar, tri-octahedral micas and pyroxene has been programmed in FORTRAN IV for a 1904 A/7600 computer. The method outlined by Deer, Howie and Zussman (1971) has been followed in calculating the numbers of ions per formula unit. Part of the program dealing with the analytical data of tri-octabedral micas has been designsd on the basis of cationic and anionic valence content of the idealized unit cell, 44 (22 in half cell) because of the uncertainty of F, Cl, and H2O contents in most analyses, specially those obtained with electron probe. In addition to the numbers of ions per formula, the computer printout of calculation includes a derived structural formula expressed in a fashion outlined by Heinrich (1946) and Deer et al. (1967). The arrange merit of groups and cations within each group in the formula is after Foster ( 1960). Several extra numerical arrays were en tared in the program to recognize the partition of R+3 cations in tetrahedral and octahedral coordination categories. The program has been written for the research workers who frequently deai with the analytical data of minerals. Comparison has been made with the computer-based procedure of Jackson, Stevens and Bowen (1967) for deriving structural formula from mineral analyses.
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