A thin sill-like body, probably andesitic, intrudes a coal seam within the Collinsville coal measures (Permian) of the Bowen basin, eastern Queensland, and is altered to albite, kaolinite, chalcedony, ankerite, siderite, calcite, and leucoxene. Textural relations suggest that it was partly crystalline when intruded. The coal was converted to coke at the contact, and coal, made plastic up to two feet from the contact, injected the coke and intrusive along cracks. Liquid tarry products were carbonized and formed masses of small spheres 1-200 microns in diameter. Gases deposited carbon in open spaces. Pyrite from the coal was mobilized to form replacements and veinlets.