Exploration Results: Reporting Sulphide Mineral Observations in Drilling Intersections
Correspondence has been received from members in recent weeks regarding the description and reporting of sulphide mineralisation in drilling samples. This relates, essentially, to sulphide intersections being reported without any attempt to:
- Describe the nature of sulphide mineral occurrence (e.g. massive, disseminated, in veins, forming veins or bands concordant or discordant with bedding or a penetrative foliation observable in the host rock);
- Identify the minerals observed; or,
- Estimate the abundances of any sulphide minerals observed.
Estimation of the proportions of mineral species present in a sample, where individual grains or crystals are visible in hand specimen, is considered to be:
- a skill in which geologists are trained during the course of their university studies in, but not confined to, mineralogy, petrology and economic geology;
- an aspect of exploration and mining work in which geologists may be readily and meaningfully trained; and,
- work that may be guided by published resource materials (e.g. mineral percentage estimation charts published in the AusIMM Field Geologists’ Manual and numerous other publications, including reference cards that may be readily accessed and referred to by geologists undertaking sample examination and description (Figure 1, Figure 2).
Figure 1. Chart or estimating the modal percentages of minerals in rocks, http://faculty.uml.edu/Nelson_Eby/89.506/Assignments/Modal%20percent%20chart.jpg, accessed 12 Sep 2015
Figure 2. Estimation of the proportion of constituents in mixtures.
http://all-geo.org/volcan01010/wp-content/uploads/2012/09/PumiceLithicsProportions.png accessed 12 Sep 2015.
Estimates by experienced, competent geoscientists are considered to be reliable and reproducible semi-quantitative estimates of the abundance of minerals present in a sample. Visual estimates of sulphide mineral abundance should, however, never be considered a proxy or substitute for laboratory analyses where metal concentrations or grades are the factor of principal economic interest. Visual estimates also potentially provide no information regarding potential impurities or deleterious physical properties relevant to valuations of some mineral commodities such as graphite and many industrial minerals. Where visual estimates are reported, Competent Persons should provide an indication of when more substantive and reliable data in the form of laboratory analyses will be available.
Further, the ability to identify economically significant minerals, comprising either a mineral of value or a potentially deleterious constituent is considered to be a required skill possessed by geoscientists acting as Competent Persons for the commodity and style of mineralisation that forms the subject of any announcement or statement of Exploration Results, Mineral Resources or Ore Reserves issued in compliance with the JORC Code (2012).
Not adequately describing mineral species present, their relative abundances and the form in which they occur when their presence in samples is included in announcements and reports of exploration results may be considered not to comply with the underlying transparency and materiality principles of the JORC Code (2012) that may constitute a breach of the Code.
The correspondence received does not constitute a complaint against any Member. The issue is, however, one within the remit of the AIG Complaints Committee to review, consult with members in relation to, and issue advice and guidance to Members.
Future failure to adequately address these requirements will expose Members acting as Competent Persons for statements of Exploration Results, Mineral Resources and Ore Reserves to complaints of being in breach of the JORC Code (2012), that may result in complaints being referred to AIG’s Ethics and Standards Committee.
Chairperson, AIG Complaints Committee
29 October 2015