Page 21 - Introduction to Mineral Exploration

4 C.J. MOON & A.M. EVANS

These minerals occur in concentrations that Gangue material is the unwanted material,
range from parts per million (ppm) to low per- minerals, or rock, with which ore minerals are
centages of the overall mineral deposit. usually intergrown. Mines commonly possess
“Industrial minerals have been defined as processing plants in which the run-of-mine
any rock, mineral or other naturally occur- (ROM) ore undergoes comminution before the
ring substance of economic value, exclusive of ore minerals are separated from the gangue
metallic ores, mineral fuels and gemstones” minerals by various processes. This provides a
(Noetstaller 1988). They are therefore minerals saleable product, e.g. ore concentrates and tail-
where either the mineral itself, e.g. asbestos, ings which are made up of the gangue material.
baryte, or the oxide, or some other compound
derived from the mineral, has an industrial
application (end use). They include rocks such 1.2.2 The relative importance of metallic and
as granite, sand, gravel, and limestone, that industrial minerals
are used for constructional purposes (these Metals always seem to be the focus of atten-
are often referred to as aggregates or bulk tion for various reasons, such as their use in
materials, or dimension stone if used for warfare, rapid and cyclical changes in price,
ornamental cladding), as well as more valuable occasional occurrence in very rich deposits
minerals with specific chemical or physical (e.g. gold bonanzas), with the result that the
properties like fluorite, phosphate, kaolinite, great importance of industrial minerals to our
and perlite. Industrial minerals are also civilization is overlooked. As flints, stone axes,
frequently and confusingly called nonmetallics bricks, and pottery they were the first earth
(e.g. Harben & Kuzvart 1997), although they resources to be exploited by humans. Today
can contain and be the source of metals, e.g. industrial minerals permeate every segment of
sodium derived from the industrial mineral our society (McVey 1989). They occur as com-
halite. On the other hand, many deposits ponents in durable and nondurable consumer
contain metals such as aluminum (bauxite), goods. The use of industrial minerals is obvious
ilmenite, chromite, and manganese, which are but often unappreciated, e.g. the construc-
also important raw materials for industrial tion of buildings, the manufacture of ceramic
mineral end uses. tables, and sanitary ware. The consumer is
The JORC definition covers metallic frequently unaware that industrial minerals
minerals, coal, and industrial minerals. This is play an essential role in numerous other goods,
the sense in which the terms mineral resource ranging from books to pharmaceuticals. In
and ore reserve will normally be employed in developed countries such as the UK and USA,
this book, except that they will be extended to but also on a world-wide basis (Tables 1.1 &
include the instances where the whole rock, 1.2), industrial mineral production is far more
e.g. granite, limestone, salt, is utilized and not important than metal production from both
just a part of it. the tonnage and financial viewpoints.
The term mineralisation is defined as “any Graphs of world production of the tradi-
single mineral or combination of minerals tionally important metals (Figs 1.1–1.3) show
occurring in a mass, or deposit, of economic interesting trends. The world’s appetite for
interest” (IMM Working Group 2001). This the major metals appeared to be almost insati-
group used the term mineral reserve for the able after World War II. Postwar production
mineable part of the mineralisation (for further increased rapidly. However, in the mid seven-
discussion see section 10.4). The Australian ties an abrupt slackening in demand occurred
Joint Reserve Committee has a similar ap- triggered by the coeval oil crisis. Growth for
proach but prefers the term ore reserve. many metals, such as copper, zinc, and iron
Another useful discussion on the economic ore, resumed in the 1980s and 1990s. Lead,
definition of ore is given by Lane (1988). This however, shows a different trend, with overall
text explains the principles of cut-off grade production increasing slightly. Mine pro-
optimization used in mining and processing. duction has declined with more than 50% of
This is an essential part of extracting max- overall production now derived from recycling.
imum value out of finite geological resources. Other factors affecting the change in growth