Classification, Distribution and Uses of Ores and Ore Deposits - Metals and Society: An Introduction to Economic Geology - page 34

passive margin, then large accumulations of dense stable minerals may build up in
beach sands. Major deposits of ilmenite, together with associated heavy minerals
such as rutile (another source of Ti), zircon (a source of Zr) and monazite (a source
of Th and the rare earth elements) occur in sands along the coasts of Australia, India
and South Africa.
Diamond also in mined in two types of deposit. The major and primary source is
kimberlite, a rare type of ultramafic rock that is emplaced as pipe-like intrusions at
or near the margins of Archean cratons. And when kimberlite is eroded, the
diamonds are released and accumulate in alluvial deposits in rivers or in sands
and gravels at the coast. In historical times most diamonds were found in alluvial
deposits in India (from a source whose location that remains unknown). Then the
major deposits in South Africa, both kimberlitic and alluvial, were discovered and
these provided the bulk of mined diamond for most of the twentieth century. In the
last decade, new deposits have been located in almost every country with a stable
Archean craton; in Russia, Australia, Canada, Brazil, Greenland and Finland.
2.4 Global Production and Consumption of Mineral Resources
The lists in Tables 2.7 and 2.8 indicate where metals and ore minerals are mined and
consumed. The first tables ranks countries in terms of their production of mineral
resources; the second the amount of the commodity they consume. Note that
petroleum is not included in the selection of commodities. Although many of
the largest countries figure near the top of each list, as is to be expected, there are
a number of anomalies that provide useful information about how the global
minerals industry functions.
In the two tables we see three different categories of countries: (1) large
industrialized countries that have large domestic mineral resources; (2) countries
with few or no mineral resources; and (3) countries with large resources but
relatively small populations or a poorly developed industrial base. The first type
of country, for which we could cite as examples Russia, USA and China, are near
the top of the list of both producers and consumers; they produce from their own
domestic sources a large proportion of the metals that that consume.
In the second category we find countries like Japan and Germany, which possess
very few domestic ore deposits but have abundant and active industry that
consumes large amounts of raw materials. These countries are major importers of
ores and/or refined metals. Finally, the countries in the last category - those
countries with large resources but small populations or underdeveloped industry -
are the major exporters of minerals (Table 2.7 ). Examples include Australia, South
Africa, Chile, Brazil and Jamaica. There are, of course, many exceptions to these
general observations. The USA, for example, produces a wide range of mineral
products but contains very few large deposits of Ni and Cr. Domestic resources of
these metals, which are essential for steel production, are totally inadequate for its
needs. The USA is therefore a major importer of Ni and Cr. The incredible