Page 248 - Introduction to Mineral Exploration

10: EVALUATION TECHNIQUES 231

Exploration Results

Mineral Resources Ore Reserves

Inferred
Increasing level
of geological
knowledge and
Indicated Probable
confidence
FIG. 10.14 A JORC Box used as an
early basis for classifying mineral
resources and reserves. It takes into Measured Proved
account the increasing degree of
confidence in the resources and the Consideration of mining, metallurgical, economic, marketing,
financial feasibility of mining legal, environmental, social and governmental factors
them. (From Australasian Joint Ore (the modifying factors)
Reserves Committee 2003.)

Nations (UNCE 2001) on a common set of mining and exploration companies. The suc-
terms to describe resources and reserves, and an cess of the Code is based upon its early adop-
international set of definitions and guidelines. tion in full by the Australian and New Zealand
Stock Exchanges, and the ability and willing-
ness of the mining industry to bring Com-
10.4.1 The JORC Code
petent Persons to account when necessary.
The JORC code sets out a system for class- The JORC Code is designed for reporting
ifying tonnage and grade estimates as either of mineral resources, which it defines as a
ore reserves or mineral resources, and of sub- concentration or occurrence of material of
dividing these into categories that reflect dif- intrinsic economic interest in or on the Earth’s
ferent levels of confidence (Fig. 10.14). The crust in such form and quantity that there are
purpose of this is purely for public reporting. reasonable prospects for eventual economic ex-
JORC does not regulate how estimates should traction. The location, quantity, grade, geolog-
be done, nor does it attempt to quantify the ical characteristics, and continuity of a Mineral
amount of data needed for each mineral Resource are known, estimated, or interpreted
resource category. from specific geological evidence and know-
A Competent Person(s) makes these deci- ledge, by a Competent Person appointed by the
sions based on direct knowledge of the deposit Company. Mineral Resources are subdivided,
in question. The criteria used may be entirely in order of increasing geological confidence,
subjective or they may involve some quantitat- into Inferred, Indicated, and Measured cate-
ive measures, or mixtures of both. There are gories. Portions of a deposit that do not have
no prescribed methods that can be applied “off reasonable prospects for eventual economic
the shelf.” It is very important that the selected extraction must not be included in a Mineral
methods of distinguishing resource classes Resource.
should be geologically sensible in the context A mineral resource is not an inventory of
of the deposit being studied. all mineralisation drilled or sampled, regard-
Stephenson (2000) explained that the JORC less of cut-off grade, likely mining dimensions,
Code has been operating successfully for over location, or continuity. It is a realistic inven-
10 years and, together with complementary tory of mineralisation, which, under assumed
developments in stock exchange listing rules, and justifiable technical and economic con-
has brought about substantially improved ditions, might, in whole or in part, become
standards of public reporting by Australasian economically extractable.