The Anatomy of a Mine - Mining and the Environment: From Ore to Metal - page 183

It is in this later exploration phase that the continuity of mineralization (or the lack of it) is
determined and the shape of the deposit and the spatial distribution of ore grades become
better dei ned. Geological resources are computed, and decisions made on continuing
exploration. It is at this stage where the difference between resource and reserves and their
sub-categories emerges ( www.insidemetals.com , see Figure 4.9 ).
Various dei nitions of the word reserves (an economic term) and resources (a geological
term) have been attempted in the past, and, with respect to the coni dence level of the esti-
mate, these dei nitions have been further rei ned by such terms as measured, indicated, and
inferred, which have commonly been used in geological estimates; or proven, probable, and
possible, which is the more readily used terminology of industry for economic evaluations.
The dei nitions introduced by the US Bureau of Mines and the US Geological Survey in 1974,
on which the following explanations are based, have achieved wide acceptance and form the
basis of the JORC code which is almost exclusively used in Australia and elsewhere in Asia.

Mineral Resource
A Mineral Resource is a concentration or occurrence of natural, solid, inorganic or fos-
silized organic material in or on the Earth's crust in such form and quantity and of such
a grade or quality that it has reasonable prospects for economic extraction. The loca-
tion, quantity, grade, geological characteristics, and continuity of a Mineral Resource
are known, estimated or interpreted from specii c geological evidence and knowledge.
A Mineral Resource, sometime also termed in situ or Geological Reserve, is made up of
inferred, indicated, and measured (proven) mineral resources.
Inferred Mineral Resource is that part of a Mineral Resource for which quantity and
grade or quality can be estimated on the basis of geological evidence and limited sampling
and reasonably assumed, but not verii ed, geological and grade continuity. The estimate is
based on limited information and sampling gathered through appropriate techniques from
locations such as outcrops, trenches, pits, workings and drill holes.
Indicated Mineral Resource is that part of a Mineral Resource for which quantity, grade
or quality, densities, shape and physical characteristics, can be estimated with a level of
coni dence sufi cient to allow the appropriate application of technical and economic

FIGURE 4.9
The Relationship Between The Various
Categories of Mineral Resources and
Mineral Reserves

KNOWLEDGE OF RESOURCE OCCURRENCE

INCREASING GEOLOGICAL CERTAINTY

Increased
Exploration
Drilling

Mineral resource is a geological term,
while mineral reserve is an economic
term. A mineral reserve is the eco-
nomically mineable part of a mineral
resource demonstrated by at least a
preliminary feasibility study.

ECONOMIC

Changes in
Technology
Changes in
Commodity
Price

NOT
ECONOMIC

IDENTIFIED UNDISCOVERED

Inferred

Measured Indicated Hypothetical Speculative

Reserves