Richard Mozley's gravity concentration legacy lives on

Although Cornwall was once the world's premier producer of copper, it will always be most associated with tin mining. Gravity concentration has always been the major method for concentrating cassiterite and many gravity devices have been developed in this small county.

In the heyday of Cornish Mining in the 18th and 19th centuries, tin ores were concentrated by buddles and round frames, developed mainly in Cornwall, and rag frames, a truly Cornish innovation (see YouTube). In the late 19th and early 20th centuries these became obsolete with the introduction of Frue Vanners developed in the USA. Frue vanners also became obsolete later in the 20th century, being replaced by another American invention, the Wilfley shaking table, which is still very much in use. The Cornish company Holman-Wilfley Ltd manufactures high-quality shaking tables for the mining and recycling industries, combining the legacies of Holman Brothers, an historic Cornish engineering firm and the Wilfley table design.

Remains of buddles at the Botallack Mines tin dressing floor

Cornish Mining  has had two world class inventors, Richard Trevithick (1771-1833), the pioneer of the high pressure steam engine, and Richard Mozley (1933-1995). A graduate of Camborne School of Mines, Richard undertook a final year project with the then head of engineering, Dr. G.H. Jones, who was working on a prototype wet high intensity separator, which evolved into the well-known Jones Separator. This sparked his passion for invention and during his time as a research fellow at Bristol University he became interested in developing gravity concentrators to treat ultrafine cassiterite in the Cornish tin mines. He developed a modern separator to replace the round frames and vanners traditionally used in Cornwall, the result being the first machine to bear his name. The Mozley Table, developed further by local company Bartles and marketed as the Bartles-Mozley Concentrator, was initially installed in the Geevor tin mine, and then in many concentrators around the world. As this was essentially a roughing or scavenging device, Richard went on to develop the Bartles Cross-Belt Separator to upgrade concentrates from the B-M Concentrator. Again this was commissioned at Geevor but was soon taken up on several chromite installations in the Philippines and Europe.

In 1975 he decided to go it alone as an independent consultant, concentrating on inventing and developing processes for recovery of fine heavy minerals. The company initially concentrated on the development of small hydrocyclones for desliming feeds to gravity concentrators, and the sand separator, a development of the conventional shaking table, which was tested at the South Crofty tin mine. This was eventually licensed to GEC Mechanical Handling as the Duplex Concentrator. The Mozley cyclones also became world famous, particularly the 1 inch and 2 inch diameter plastic hydrocyclones assembled in a high-capacity housing.

I particularly remember Richard talking enthusiastically, over a few beers, about his latest invention, a shaking table wrapped through 360 degrees into a circular drum which was not only shaken, but rotated to produce a high-G force - one of the first of the enhanced gravity concentrators, which competed with the Knelson and Falcon concentrators. The Mozley Multi Gravity Separator (MGS) was tested at the Wheal Jane mine, under the supervision of concentrator superintendent Mike Hallewell, and then showcased at the 1988 IMPC in Stockholm. The device has been used successfully around the world for the recovery of ultrafine heavy minerals, and soon made the B-M and Duplex Concentrators redundant.

Stockholm 1988, the MGS demonstrated by Billy Chan, Don Hepburn and Richard Mozley

Building upon the legacy of Richard Mozley, Cornish company Gravity Mining continues to innovate and refine this technology for fine and ultra-fine mineral recovery.​ The MGS has evolved in the hands of the company, but I was amazed to see its latest incarnation, the C910 Multi Gravity Separator, which was showcased at the company's new site at Blackwater, near Redruth, a couple of weeks' ago. This massive machine has been specifically designed for bulk commodities such as iron ore or chromite, where ultrafine minerals are often lost to tailings. I expect to hear much more of this impressive device and particularly hope to hear of developments at next year's Physical Separation '26 in Cape Town.

Gravity Mining Directors Colin Colino, Treve Mildren and David Mildren with the C910 MGS