Mineral processing is a critical enabling technology in the establishment and maintenance of material civilisation. As in other fields, the technology of mineral processing has evolved over time. This paper considers some of the forces driving these changes and the ways in which invention and innovation happen in mineral processing. Invention, the process of creating something new, is distinguished from innovation, the process of introducing something new. Both are needed if new ideas are to be realised in practical engineering terms and applied to generate wealth. Four case studies are considered in which lone inventors tackled the problem of improving fine mineral gravity concentration. Some general Issues relating to invention and innovation in corporate or institutional laboratories are also discussed. It is concluded that, although invention is a very diverse phenomenon there are some features that are common to many successful innovations. These include need, a driving force, time (10-15 years is a common period from idea to technical maturity), vision, perseverance, faith, long-term support (financial and otherwise) and a willingness to take risks. The probability of success is also greatly enhanced if there is a fruitful alliance between inventor and customer.