Coal petrographic methods used to characterize coals for industrial purposes have further application in the interpretation of environments of deposition through the plotting of maceral data that have been grouped on the basis of mutual abundance using correlation coefficients. Huminite (or vitrinite), exinite, inertinite ternary diagrams do not readily distinguish environmental conditions during peat deposition because the three categories of macerals are based on broad ranges of reflectance. Macerals within each group are not genetically related. Lignite cores from Neshoba County, Mississippi, having an undetermined depositional environment, have been analyzed petrographically. Petrographic data from other Gulf Coast lignites of known environments of deposition (determi ed by nonpetrographic means) were grouped using the genetically discrete maceral associations formed by combining macerals that correlate with each other. These genetically discrete maceral groups are termed "lithogroups." When maceral data are plotted on ternary diagrams by lithogroups, the plot reveals fields that are characteristic of particular environments of deposition. The Neshoba lignites overlap in the fluvial/deltaic region of the ternary plot. An important factor controlling peat composition is thought to be pH, thereby affecting the petrography of the resulting coal.

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