Detailed analyses of coal ash deposits were performed with the use of SEM, X-ray, and image analysis in order to characterize local deposit properties as a function of position. Such analyses are important for understanding and predicting the thermal and physical properties of ash deposits. The present study used measurements of deposit composition and morphology to identify four characteristic regions in the deposits: the initial region, adjacent region, middle region, and outer region. These regions were used as a basis for quantitative description of the transitions which occur from the particulate initial layer to the highly sintered outer layer. Detailed properties of each of these regions are presented and discussed. Understanding developed from this characterization provides a basis for the development and validation of predictive models of the deposition process.