Crystalline Phases in Fired Shale Products

The development of crystalline and glassy phases was traced in shale specimens fired over a range of temperatures. Two raw materials of distinctly different compositions were selected far study, namely; a high‐lime shale and an argillaceous shale. Mechanical separations and X‐ray analyses were used to isolate and identify the crystalline phases, whereas the development of glass was observed petrographically. The identification of the phases at various heat‐treatments was helpful in explaining the properties of fired shale products.