Mincalc 1--a Spreadsheet for the Rapid Calculation of 2:1 Phyllosilicate Mineral Formulae from Chemical Analyses

The accurate calculation of clay mineral formulae from chemical analyses is important because the identity of the mineral as well as its exchange properties can be readily determined from its formula (Jackson 1969). Unfortunately, many mathematical steps, all fraught with possible errors, are required to carefully convert the data from either an oxide or metal basis to the structural formula. For one analysis, hand calculations are not that ditiicult to perform and, if done carefully, will yield the accurate formula. However, the time-effectiveness of hand calculations is severely dampened when determining more than one analysis. Because several analyses may be required to fully characterize the minerals in a sample, a spreadsheet program that can quickly and accurately determine the structural formulae for these analyses would be beneficial. To this end, a spreadsheet program, n a m e d MINCALCI, that performs these structural formulae calculations for 2:1 phyllosilicates from the chemical data was developed. MINCALC 1 has been tested using many chemical analyses and structural formulae calculations from the clay mineral literature. Because the spreadsheet was designed using charge occupancy rather than atom occupancy for the octahedral layer, the structural formulae of both dioctahedral and trioctahedral minerals can be quickly and accurately calculated.