Diamond July17

The following characteristics of diamond deposits are different from those of typical metalliferous and coal deposits, and they emphasise the need for a Diamond-specific Code.

  • The widely differing nature of diamondiferous deposits and their associated forms of mineralisation and the estimation relevant to these;
  • The (very) low diamond content of primary and placer diamond deposits and their variability;
  • The particulate nature of diamonds and individual physical characteristics, which have a significant impact on diamond value. These characteristics are size and assortment, the latter being comprised of model (shape or morphology), quality and colour;
  • For diamond exploration programmes, Exploration Targets, Mineralisation, Resources and Reserves, the term ‘quality’ cannot be used as a substitute for ‘grade’;
  • The specialised field of diamond valuation; and
  • The relationship between average diamond value and the underlying diamond size distribution.

As a result of the above characteristics, diamond deposits rarely achieve Measured Resource status. This impacts significantly upon the classification of Proved Reserves (see also Clauses 69 and 71). The sampling and estimation of marine placer deposits is particularly difficult and expensive and, thus, even the assignment of Indicated status may prove difficult.

The SAMREC Code has a detailed diamond-specific section comprising Clauses 60-72; a diamond-specific section to Table 1 (Section 11). In addition, a stand-alone Guideline Document has been prepared which provides the methodologies and definitions of the relevant terms that should be considered in the preparation of reports on Diamond Exploration Targets, Diamond Resources and/or Diamond Reserves. Specific inclusions include guidance on the use of Kimberlitic Indicator Minerals (KIM’s), microdiamonds and the valuation of diamond parcels for revenue estimation. It also provides a guide table of contents to assist with the compilation of Competent Persons Reports (CPR’s).

The Diamond Guidelines are applicable to other Gemstones as well. It is expected that the CP will be able to adapt the specifics of the Code to the particular situation, while still adhering to the basic principles. Various industry specific recommendations exist outside of this forum for the classification of, inter alia, tanzanite, emerald and rubies/sapphire deposits. CPs are encouraged to familiarise themselves with these and refer to them, where appropriate.