Micaceous haematite, or micaceous iron oxide (MIO), was found to make excellent anti-corrosion paint. In later years virtually all the output from Kelly Mine and other MIO mines was used for this purpose. With the rapid expansion in the industrial uses of steel, mining activity at Kelly Mine greatly increased, the paint finding use on major structures such as warships for the Admiralty and the Royal Albert Bridge at Saltash for the Great Western Railway. The paint colour - Battleship Grey - takes its name from this paint. Nowadays MIO paint is a widely available excellent quality protective paint, as a search of the internet will reveal. Modern use extends to such structures as bridges, pylons, electrical distribution equipment and oil rigs; at Kelly Mine it is used to protect the pipe to the water turbine!

Nowadays, MIO is mined many countries: Austria, Turkey, Spain,Australia, etc. The quality of the MIO tends to vary and the softest material makes the best paint.

A paint has three components:

Micaceous haematite has a laminar or flaky structure and the individual flakes are inert and impervious to ultraviolet light and the pollutants which cause corrosion.

When an MIO paint, using micaceaous haematite as the pigment, dries or cures on a surface, the haematite flakes orientate themselves into layers more or less parallel to the surface. This results in interleaving and overlapping somewhat similar to fish-scales or roof tiles, resulting in a tight seal which acts as an effective barrier to corrosion from water, sea-spray, sulphur dioxide, ammonia and other pollutants; they cannot permeate the packed layered structure of the paint. MIO flakes are also impervious to ultraviolet light therby greatly reducing deterioration of the binding medium.

Thus MIO paint is an excellent anti- corrosion even by todays exacting standards.