Inorganic polymers, more commonly referred to as "geopolymers", are alumino-silicate materials which exhibit excellent physical and chemical properties and a diverse range of potential applications, including precast structures and non-structural elements, concrete pavements and products, containment and immobilisation of toxic, hazardous and radioactive wastes, advanced structural tooling and refractory ceramics, and fire resistant composites used in buildings, aeroplanes, shipbuilding, racing cars, and the nuclear power industry. The current paper presents a brief history and a review of geopolymer technology, summarises and critically analyses the most important research findings over the last 25 years, attempts to elucidate chemistry and reaction mechanisms for the most important categories of materials involved, identifies the gaps in the existing body of knowledge and underlines the reasons why this promising technology after all these years of research has not become widely accepted by the industry. Finally the paper proposes further research and development topics and suggests steps forward to improve the potential of geopolymerisation, focusing on the utilisation of mining and metallurgical wastes and by-products, the synthesis of geopolymers with advanced properties and the stabilisation of hazardous wastes. It is strongly believed that geopolymerisation, when established as a viable technology and recognised by the industry, will contribute to the sustainable development of the minerals sector. (c) 2007 Elsevier Ltd. All rights reserved.