Abstract

A summary of existing petrographic studies on Wyoming coal beds shows changes in the style of petrography. Authors have gradually incorporated new methodologies such as macroscopic petrography together with microscopic, the use of oxidative etching to improve differentiation of petrographic entities and the inclusion of non-petrographic data (sedimentology, palynology, coal chemistry) with petrography as an aid in interpreting depositional environments or in assessing a coal's potential uses. However, at least two major problems still exist for petrographic study of Wyoming coal; sampling and analytical methods are inappropriate for thick coal beds and microscopic petrographic results cannot be compared with data from peat, the modern analogue of coal. It is suggested that the time and effort required for sampling and petrographic analysis of thick coal beds can be reduced by the use of stratified sampling of macroscopically defined units together with collection of block, rather than channel samples. In addition, the microscopic petrography of coal can be compared to that of peat when botanical components are identified on block samples of coal, rather than maceral entities being identified on particulate pellets.