No abstract

The morphology of massive and framboidal pyrites and marcasite extracted from lignitic cores was examined with light and scanning electron microscopes. The primary objective was to determine the surface area for these sulfide minerals. Framboidal pyrite spheres consisted of micron‐sized crystals and suggested a high surface area compared to other iron (Fe) sulfides. Specific surface space was determined using the linear form of the B.E.T. equation and N2 gas as the adsorbate.Framboidal pyrite was composed of individual microcrystals that ranged from 1 to 5 µm in diameter. Surface area of framboidal pyrite remained near 2.0 m2/g for mean diameters ranging from 150 to 60 µm but increased to as high as 4.0 m2/g for diameters between 5 and 2 µm. Marcasite spheres were 4 to 5 times larger in diameter than single framboids. Surface area of all fractions of marcasite and massive pyrite ranged from 0.2 to 0.5 m2/g. Specific surface decreased as particle size increased.

Distribution of sulfur and its three predominant forms in 10 lignitic coal seams developed in fluvial environments in east Texas was examined. The average sulfur content for individual seams varied from 0.88 to 3.98%, while the total sulfur content of 10‐cm sections of these seams varied from 0.53 to 16.79%. Sulfate sulfur was a minor component compared to pyritic or organic sulfur. The organic sulfur content determined by the standard American Society for Testing and Materials (ASTM) procedure as the difference between the inorganic sulfur (sulfate + pyritic sulfur) and the total sulfur in the original material, in general, remained uniform within a given lignite profile. A significant correlation was obtained between the organic sulfur content obtained by the ASTM procedure and a more direct method of density separation of specific gravity < 1.6 fraction and the determination of total sulfur in this fraction with an induction furnace and automatic titrator. Pyritic sulfur had the most variable distribution with a greater concentration of pyrite occurring at the seam fringes, which suggests the need for separate handling of these highpyrite content mine spoils for safe disposal.