| Confidence Reef | |
|---|---|
 | |
| Type | Heritage Site |
| Nearest city | Roodepoort, South Africa |
| Coordinates | 26°08′09″S27°52′55″E / 26.135810°S 27.882030°E |
| Founded | 1884 |
| Founder | Fred Pine Theophilus Struben |
Confidence Reef is a historical gold-bearing quartz vein situated within the Kloofendal Nature Reserve, in close proximity to Roodepoort, South Africa.
The Confidence Reef was discovered by Fred Pine Theophilus Struben and his brother, Harry Struben, on September 18, 1884, on the farm Wilgespruit in Roodepoort, Johannesburg. This discovery was pivotal in sparking a gold rush to the Witwatersrand region, which eventually led to the discovery of the Main Reef in 1886. The Struben brothers were the first to extract payable gold from the Witwatersrand. [1]
The Confidence Reef is notable as the first site of a payable gold discovery on the Witwatersrand, an event that contributed to the establishment of Johannesburg, the "City of Gold.'' The discovery spurred the development of other major gold mines, including the Main Reef in 1886, one of the richest gold-bearing areas in history. This find also led to the creation of the Witwatersrand Gold Mining Company, along with others like the Jubilee and Langlaagte mines. The techniques and infrastructure introduced during this early phase, such as stamp mills for ore processing, formed the foundation for modern mining practices and facilitated Johannesburg's rise as a major global player in the gold industry. [1]
The Confidence Reef is part of the larger Witwatersrand Basin, which is renowned as one of the richest goldfields in the world. The basin is made up of complex sedimentary rock formations deposited around 2.9 to 2.7 Ga in the Mesoarchaean era. [2] [3]
The Witwatersrand Basin's sedimentary layers consist of conglomerates, quartzites, and shales that were deposited in a shallow marine environment. These rock sequences, which can exceed 7,000 m in thickness, contain gold-bearing conglomerates formed through mechanical reworking of sediments and microbial fixation. [3]
The origin of the gold within the Witwatersrand Basin is thought to be a combination of placer deposition and hydrothermal processes. Gold deposits are concentrated at the base of fluvial cycles within the Central Rand Group, with ancient microbial activity playing a role in the fixation of organic materials and enhancing gold concentration. [4] This Gold is found in ancient sedimentary rocks, primarily in conglomerates. The unique gold mineralization processes in this basin have been the subject of much debate, with two primary theories dominating the discussion: the placer theory and the hydrothermal theory. Both of these processes are thought to have contributed to the important gold concentration in the area. [5]
The placer theory suggests that gold originated from ancient greenstone belts surrounding the Witwatersrand Basin. Rivers carried gold-rich sediments from these areas, depositing them in alluvial fans and river channels. Over time, the gold settled into the basin's conglomerate layers, which were formed by fluvial processes during the Mesoarchaean era [5] [6]
The hydrothermal theory suggests that gold was introduced or remobilized in the Witwatersrand Basin by hot, mineral-rich fluids that permeated the basin after the sediments had been deposited. [6] [7]
Several tectonic events, including faulting and folding, shaped the Witwatersrand Basin. The Vredefort impact, one of Earth's largest meteorite impacts, also altered the distribution of gold, remobilizing the mineral within the basin's sedimentary layers. Further geological processes, such as the intrusion of the Bushveld Igneous Complex, introduced heat that facilitated additional gold mobilization. [3] [4]
The Struben brothers were engaged in active mining operations at Confidence Reef until 1888, extracting gold from a quartz vein that they had discovered. Following their departure, the site retained its importance within South Africa's mining history. In 1935, Fred Struben's wife, Mabel, sold the area to George Brown, who proceeded to continue mining operations on the site. With the passage of time, the importance of the Confidence Reef grew, not only in terms of its role in mining activities but also in relation to its status as a site of South African heritage. [1]
In recognition of its historical value, the Confidence Reef Mine was proclaimed a national monument in 1980. This designation showed the importance of the early gold mining efforts that contributed to the later development of the Witwatersrand Gold Rush. The Confidence Reef is located within the Walter Sisulu National Botanical Garden in Roodepoort, South Africa, making it accessible for educational visits and a reminder of the country's rich mining heritage. [1]
In 1936, George Brown erected a monument to commemorate the Struben brothers' contribution to the discovery of the gold-bearing conglomerates in the Witwatersrand. This monument, located at the Confidence Reef site, honors their role in the birth of Johannesburg and South Africa's gold industry. [1]
Ore is natural rock or sediment that contains one or more valuable minerals, typically including metals, concentrated above background levels, and that is economically viable to mine and process. The grade of ore refers to the concentration of the desired material it contains. The value of the metals or minerals a rock contains must be weighed against the cost of extraction to determine whether it is of sufficiently high grade to be worth mining and is therefore considered an ore. A complex ore is one containing more than one valuable mineral.
In geology, a placer deposit or placer is an accumulation of valuable minerals formed by gravity separation from a specific source rock during sedimentary processes. The name is from the Spanish word placer, meaning "alluvial sand". Placer mining is an important source of gold, and was the main technique used in the early years of many gold rushes, including the California Gold Rush. Types of placer deposits include alluvium, eluvium, beach placers, aeolian placers and paleo-placers.
The Witwatersrand is a 56-kilometre-long (35 mi), north-facing scarp in South Africa. It consists of a hard, erosion-resistant quartzite metamorphic rock, over which several north-flowing rivers form waterfalls, which account for the name Witwatersrand, meaning 'white water ridge' in Afrikaans. This east-west-running scarp can be traced with only one short gap, from Bedfordview in the east, through Johannesburg and Roodepoort, to Krugersdorp in the west.
Skarns or tactites are coarse-grained metamorphic rocks that form by replacement of carbonate-bearing rocks during regional or contact metamorphism and metasomatism. Skarns may form by metamorphic recrystallization of impure carbonate protoliths, bimetasomatic reaction of different lithologies, and infiltration metasomatism by magmatic-hydrothermal fluids. Skarns tend to be rich in calcium-magnesium-iron-manganese-aluminium silicate minerals, which are also referred to as calc-silicate minerals. These minerals form as a result of alteration which occurs when hydrothermal fluids interact with a protolith of either igneous or sedimentary origin. In many cases, skarns are associated with the intrusion of a granitic pluton found in and around faults or shear zones that commonly intrude into a carbonate layer composed of either dolomite or limestone. Skarns can form by regional or contact metamorphism and therefore form in relatively high temperature environments. The hydrothermal fluids associated with the metasomatic processes can originate from a variety of sources; magmatic, metamorphic, meteoric, marine, or even a mix of these. The resulting skarn may consist of a variety of different minerals which are highly dependent on both the original composition of the hydrothermal fluid and the original composition of the protolith.
The Vredefort impact structure is the largest verified impact structure on Earth. The crater, which has since been eroded away, has been estimated at 170–300 kilometres (110–190 mi) across when it was formed. The remaining structure, comprising the deformed underlying bedrock, is located in present-day Free State province of South Africa. It is named after the town of Vredefort, which is near its centre. The structure's central uplift is known as the Vredefort Dome. The impact structure was formed during the Paleoproterozoic Era, 2.023 billion years ago. It is the second-oldest known impact structure on Earth, after Yarrabubba.
The Witwatersrand Gold Rush was a gold rush that began in 1886 and led to the establishment of Johannesburg, South Africa. It was a part of the Mineral Revolution.
Roodepoort is a city in the Gauteng province of South Africa. Formerly an independent municipality, Roodepoort became part of the Johannesburg municipality in the late 1990s, along with Randburg and Sandton. Johannesburg's most famous botanical garden, Witwatersrand National Botanical Gardens, is located in Roodepoort.
Harmony Gold is the largest gold mining company in South Africa. Harmony operates in South Africa and in Papua New Guinea. The company has nine underground mines, one open-pit mine and several surface operations in South Africa. In Papua New Guinea, it has Hidden Valley, an open-pit gold and silver mine and a 50% interest in the Morobe Mining Joint Venture, which includes the Wafi-Golpu project and extensive exploration tenements. Outside the joint venture, Harmony's own exploration portfolio focuses principally on highly prospective areas in Papua New Guinea.
The Bushveld Igneous Complex (BIC) is the largest layered igneous intrusion within the Earth's crust. It has been tilted and eroded forming the outcrops around what appears to be the edge of a great geological basin: the Transvaal Basin. It is approximately two billion years old and is divided into four limbs or lobes: northern, eastern, southern and western. It comprises the Rustenburg Layered suite, the Lebowa Granites and the Rooiberg Felsics, that are overlain by the Karoo sediments. The site was first publicised around 1897 by Gustaaf Molengraaff who found the native South African tribes residing in and around the area.
Various theories of ore genesis explain how the various types of mineral deposits form within Earth's crust. Ore-genesis theories vary depending on the mineral or commodity examined.
In geology, a vein is a distinct sheetlike body of crystallized minerals within a rock. Veins form when mineral constituents carried by an aqueous solution within the rock mass are deposited through precipitation. The hydraulic flow involved is usually due to hydrothermal circulation.
Sedimentary exhalative deposits are zinc-lead deposits originally interpreted to have been formed by discharge of metal-bearing basinal fluids onto the seafloor resulting in the precipitation of mainly stratiform ore, often with thin laminations of sulfide minerals. SEDEX deposits are hosted largely by clastic rocks deposited in intracontinental rifts or failed rift basins and passive continental margins. Since these ore deposits frequently form massive sulfide lenses, they are also named sediment-hosted massive sulfide (SHMS) deposits, as opposed to volcanic-hosted massive sulfide (VHMS) deposits. The sedimentary appearance of the thin laminations led to early interpretations that the deposits formed exclusively or mainly by exhalative processes onto the seafloor, hence the term SEDEX. However, recent study of numerous deposits indicates that shallow subsurface replacement is also an important process, in several deposits the predominant one, with only local if any exhalations onto the seafloor. For this reason, some authors prefer the term clastic-dominated zinc-lead deposits. As used today, therefore, the term SEDEX is not to be taken to mean that hydrothermal fluids actually vented into the overlying water column, although this may have occurred in some cases.
Uranium ore deposits are economically recoverable concentrations of uranium within Earth's crust. Uranium is one of the most common elements in Earth's crust, being 40 times more common than silver and 500 times more common than gold. It can be found almost everywhere in rock, soil, rivers, and oceans. The challenge for commercial uranium extraction is to find those areas where the concentrations are adequate to form an economically viable deposit. The primary use for uranium obtained from mining is in fuel for nuclear reactors.
Mponeng is an ultra-deep tabular gold mine in South Africa in the Witwatersrand Basin of the Gauteng Province. Previously known as Western Deep Levels No1 Shaft, the mine began operations in 1986. It is one of the most substantial gold mines in the world in terms of production and magnitude, reaching over 4 kilometres (2.5 mi) below the surface. At this depth Mponeng takes the title of world's deepest mine from ground level, with aims to deepen the mine beyond 4km in order to reach more reserves. A trip from the surface to its deepest point takes over an hour. An Ecuadorian marathon runner completed a half marathon within the mine in 2017. The mine supports a very large number of people, companies and industries, including entire towns and cities.
Simmer and Jack Mines Ltd is a South African company which was founded in 1887 by the German August Simmer and Scotsman John Jack, shortly thereafter selling the majority shareholding to Gold Fields of South Africa Ltd. The company was listed until 2013 at the Johannesburg Stock Exchange.
Harry Struben, born Hendrik Wilhelm Struben and also known as Henry William Struben, was a South African randlord. He was the brother of Frederick Struben; together they managed the first gold-mining operation on the Reef. They were the sons of Johan Marinus Struben, a South African Republic official, and his wife Frances Sarah Beattie of Scottish origin. Harry was born during a yacht trip along the Lower Rhine. His family emigrated to Pietermaritzburg in Natal in 1850, and moved to Pretoria five years after.
The Free State Gold Rush was a gold rush in Free State, South Africa. It began after the end of World War II, even though gold had been discovered in the area around the year 1934. It drove major development in the region until the mid–to–late 1980s as part of the mineral revolution in South Africa.
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