Mineralogy

At every stage during the life cycle of a mineral deposit, from exploration to resource evaluation, mine planning, plant design and operation, product quality control, and through to closure and site rehabilitation, the information from mineralogical investigations should form an integral part of the knowledge base related to the resource.

Provenance Studies

In 2008, the South African Diamond and Precious Metals Regulator (SADPMR) established the Diamond Provenance Laboratory within Mineralogy. The aim of the laboratory was the creation of a database of fingerprints of rough diamonds from the African continent. This, in light of the plight of blood diamonds from the Continent. The laboratory hosts an optical stereomicroscope, camera and processing software, a Fourier transform infrared spectrometer (FTIR) and laser ablation inductively coupled plasma mass spectrometer (LA-ICP-MS). Fingerprinting of rough diamonds occurs in three stages: non-destructive optical descriptions and FTIR and destructive LA-ICP-MS. Optical observations allow the description of diamonds in terms of their physical characteristics including colour, shape, size, surface features and inclusions. Fourier transform IR allows for the determination of the concentration of nitrogen (N) in the structure of a diamond as well as determining the concentration of N present. Determining this allows the discrimination between Type I (N-bearing) and Type II (non-N-bearing) diamonds. Laser ablation is a solid sampling tool that removes a small portion of diamond (50µm diameter crater) to be analysed by the ICP-MS. The technique is destructive only in the sense that it leaves behind small craters on the surface of the diamond being analysed. The concentration of trace elements in that small portion are determined in the ICP-MS, usually at concentrations in the ppm range.

 

Coltan, cassiterite and wolframite – also conflict minerals – are routinely fingerprinted in the laboratory. These minerals are analysed by LA-ICP-MS with the aim of assigning a chemical signature to these conflict minerals from the Democratic Republic of the Congo. More routine analyses can be undertaken with the instrumentation in the laboratory such as determining the trace element concentration of specified elements in a range of matrices (including sulfates and phosphates) by LA-ICP-MS and the study of minerals and their elemental bonds by FTIR