The composition of refuse-derived char (RDC) generated by thermolysis of municipal solid waste (MSW) was studied to provide a detailed phase-mineral and chemical characterization of RDC and RDC ash. The examined RDC has main chemical characteristics similar to some subbituminous and bituminous coals, but seems to be enriched in ash and N, and depleted in VM, H and S. The high-temperature ash of RDC belongs to calsialic coal ashes abundant in P and Ti. This char is a complex mixture of intimately mixed original and newly formed organic and inorganic constituents with fluid inclusions. The organic matter consists of slightly changed and char (semicoke and coke) components generated from paper, wood, textile, plastic materials, food remains and other organic products in MSW. The major inorganic phases and minerals identified in the RDC are generally quartz, calcite, glass, kaolinite, talc, illite, muscovite, zeolite, K-feldspar, chlorite, magnetite, hematite, rutile, gypsum, halite and apatite. A number of minor (vermiculite, plagioclase, montmorillonite, sepiolite, corundum, anhydrite, barite, hydrophilite, aluminium and alloys) and accessory (cristobalite, biotite, wollastonite, goethite, spinel, portlandite, brucite, jarosite, hexahydrite, ettringite, thenardite, Na-K-Mg-Fe chlorides, dolomite and ankerite) mineral phases are also present in RDC. Modes of occurrence, abundance and some genetic features of the minerals and phases found are described and summarized. The behaviour of minerals, phases, major and minor elements during the thermolysis of MSW and combustion of RDC (500-1200 degrees C) is also discussed.