Frequently asked questions

Layered sedimentary rock, containing gravel, formed by the transport of water. Finer sediments, such as such as sand, silt, or clay fill the interstices between pebbles.

Cut-off gold grade is the minimum grade required in order for gold-bearing ore to be economically mined and processed. Material found to be above this cut-off grade is considered to be ore, while material below this grade is considered as waste.

Cut-off uranium grade is the minimum grade required in order for uranium-bearing ore to be economically mined and processed. Material found to be above this grade is considered as ore, while material below this grade is considered as waste.

The thickness of the reef zone in centimetres, multiplied by the gold grade in gramme per tonne. The unit is cmg/t.

In mining, gold grade is used as a measure of the concentration of gold in the raw material obtained from mining (= ore). It is mostly expressed as gramme of gold per tonne of ore. The unit is g/t.

It can also be expressed as a fraction of the ore, such as ‘number of gold parts per million parts of ore’, such as one part per million (or, 1 ppm). As 1 gramme is one millionth of a tonne, it follows that 1 ppm of gold is equal to 1 g/t of gold.

Half-life (symbol t½) is the time required to reduce to half of the initial value. In nuclear physics, it is applied to describe how quickly unstable atoms undergo radioactive decay, or how long stable atoms survive. For instance, the naturally occurring isotope uranium-238 has a half-life of 4.51 billion years.

This means that it would take 4,51 billion years for uranium-238 to decay into a ratio of half uranium-238 and half thorium-234

Rocks which have been subjected to heat, pressure, hot mineral-rich fluids passing through it, or, a combination of these three conditions.

The grade below which the mining of ore is taking place at a loss. Mining below the pay limit may be chosen for technical motives, tax reasons or to exploit reserves to the maximum.

Iron-rich mineral, commonly present in the Basin, with higher concentrations found in conglomerates. It occurs as primary (transported by water) or secondary form (recrystallised). The chemical formula is FeS2.

Sandstone which has undergone metamorphism. Quartzites in the Basin vary from soft and pliable, to hard and brittle.

Local term used to define gold- and uranium-bearing conglomerates which have economic potential. Rarely, quartzites often containing large concentrations of pyrite, contain significant concentrations of gold and uranium and are also termed ‘reef’ in that context.

The South African Code for the Reporting of Exploration Results, Mineral Resources and Mineral Reserves sets out minimum standards, recommendations and guidelines for Public Reporting of Exploration Results, Mineral Resources and Mineral Reserves in South Africa. It has been drawn up by the SAMREC Committee of the SAMCODES Standards Committee under the joint auspices of the Southern African Institute of Mining and Metallurgy and the Geological Society of South Africa.

The SAMREC Code is one of 11 members of CRIRSCO, the international family of international mineral reporting codes. Internationally, the different Codes have common definitions and the reporting framework which are identical, making reporting in these codes equivalent.

For more details: https://www.samcode.co.za/samcode-ssc/samrec

The SAMVAL Code in South Africa is applied in the valuation and reporting of all styles of solid mineralisation. The guiding philosophy and intent of the SAMVAL Code is that Mineral Asset Valuations should be undertaken by Competent Mineral Asset Valuators and all relevant information should be fully disclosed (SAMVAL, 2016).

The SAMVAL Code is a principles-based code meaning that the Competent Valuator must follow and base their professional judgements on the fundamental principles of the SAMVAL Code. The Code differentiates between fundamental principles which must be adhered to and guiding principles which are more ethics-based. The vital principles of materiality, transparency, competence and reasonableness must be applied by the Competent Valuator when conducting a valuation and are clearly in the SAMVAL Code: https://www.samcode.co.za/samcode-ssc/samval

Rocks formed by the accumulation and consolidation of mineral fragments that have been deposited by water, ice, and/or wind. In the Basin, all sedimentary rocks are consolidated and have undergone metamorphism.

Vertical excavation that has been lined by reinforced concrete. Shafts have different functions. Production shafts are utilised for the transport of humans, material and rock. Modern shafts have concrete headgears, while older ones have steel headgears. A typical production shaft in the Welkom Goldfield has a diameter of approximately 10 metres and has several compartments. Another function of shafts include ventilation for underground workings. Each mine should have access to at least two shafts, where the secondary shaft acts as an alternative escape route during incidents or calamities.

Local term used for an underground site where mining of the ore is taking place.

Local term used for ‘mining’.

Uranium is a silvery grey, weakly radioactive metal. It has a hardness of 6 (can scratch glass). It is malleable, ductile, strongly electropositive and a poor electrical conductor. Uranium metal has a very high density of 19,1 g/cm3 (19,1 times as heavy as water) and reacts with almost all non-metal elements (except the noble gases) and their compounds. Uranium dioxide, UO2, is produced during the extraction process of uranium-bearing ores. The Beisa Reef on Sunshine’s Beisa Project, mostly contains the mineral uraninite, the most favourable of uranium minerals to be processed in uranium plants, resulting in maximum extraction rates. Another uranium mineral in the Beisa Reef is coffinite, albeit occurring at low concentrations.

Radioactivity decays by emitting an alpha particle. Naturally occurring uranium is composed of three major radioactive isotopes, uranium-238 (>99.2% natural abundance, with a half-life of ±4.5 billion years), uranium-235 (±0.72%, with a half-life of just less than 704 million years) and uranium-234 (0.005%).

Because of the fact that U-238 is non-fissile (it cannot sustain a chain reaction in a nuclear reactor) it needs to undergo a process of enrichment to produce U-235, which is fissile. In sufficient concentration, U-235 delivers continued nuclear chain reactions, which generates heat in nuclear reactors for the generation of pressurised steam. The steam is engaged to turn large turbines that drive magnetic generators for the production of electricity.

The thickness of the reef zone in centimetres, multiplied by the uranium grade of triuranium octoxide, U3O8, in kilogram per tonne. The unit is written as cmkg/t.

A measure that is commonly utilised in South Africa, is kilogram of U3O8 per tonne of ore. It expresses the concentration of U3O8 in the raw material obtained from mining (= ore). The unit is kg/t.

Internationally, uranium grade is more often expressed as parts of U3O8 per tonne of ore (parts per million, or ppm), or as a percentage. For instance, 1 000 ppm of U3O8 = 0,1% of U3O8 = 1 kg/t of U3O8.

Gold was first discovered in 1886 on the farm Langlaagte in Johannesburg. The rocky outcrop in Johannesburg forms the Witwatersrand Ridge (“Rand” in Afrikaans), from which the Basin and its rocks derive their name. It was soon found that the gold-bearing conglomerate continued in depth and that it is part of a major sedimentary system. A major gold rush ensued and several gold mines were developed in a very short time along a strike of circa 50 km, known as the “Central Rand Goldfield”.

The Witwatersrand Basin (or, Basin) is mostly covered, and only surfaces (= ‘crops out’) in Johannesburg and around Klerksdorp. The Basin does not outcrop in the Free State Province, where Sunshine’s Beisa Project is located. It has since been established that the large parts of the original Basin has been removed by erosion and that the remaining succession of rocks form the mostly underground “Witwatersrand Basin” as it is known today. It covers an elliptical area with a ±350 km long axis from Evander in the northeast to Theunissen in the southwest, and a ±150 km short axis, from Steynsrus in the southeast to Coligny in the northwest. Subsidiary basins were also formed. The Basin contains the world’s largest gold reserves and has produced more than 50 000 tonnes of gold (or ±1 550 Moz). Witwatersrand ores have been known for their high gold grades, large tonnages and continuity over hundreds of kilometres. The Basin consists of an almost 8 km-thick layer of Archaean-age rocks which were deposited from nearly 3 billion years ago, over a period of ±260 million years.

Geologically, the Basin is called the Witwatersrand Supergroup, and consists of the lower West Rand Group and the upper Central Rand Group. The two groups are popularly called ‘Lower Wits’ and ‘Upper Wits’. The former consists mostly of shales, with subordinate quartzites and generally, low-grade gold and uranium conglomerates, while the former mostly consists of quartzites and high-grade gold and uranium conglomerates, from which circa 95% of South Africa’s gold originates. The gold- and uranium-bearing reefs on Sunshine’s two Projects in the Free State are situated in the high-grade Central Rand Group.

Higher gold grades occur mostly along a discontinuous band along the northern and western margins of the Basin. Lower gold grades are present along the remainder of all the ancient shores, around the entire Basin. Seven goldfields where almost all the gold was mined, occur where well-developed fan deltas and braided river systems were formed. The Welkom Goldfield, where Sunshine’s two Projects are located, has produced the second most gold (nearly 320 Moz), slightly less than the East Rand Goldfield (±325 Moz). At some mines, mining takes place at depths of more than 4 km. Apart from gold, uranium, silver and iridium can be recovered as by-products in extraction plants.

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