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* The following passage is a written
account of the area in 1951
:: The Pilgrim's Rest Mining District
That portion of the Pilgrim's Rest Mining District which is discussed here includes the Sabie, Graskop, and Pligrim's Rest areas. Gold was first discovered in 1872 near Sabie on the slopes of Spitzkop and a year later was also found at Mac-Mac and Pilgrim's Rest where the Creek was "rushed" in 1874.
With the exhaustion of the richer portions of the Pilgrims Creek and the discovery of gold at Barberton and, later, on the Witwatersrand, mining activities in the area declined and the workings moved from the alluvial gold in the creeks to the interbedded reefs on the hillsides. Here, the individual miner soon ran into difficulties and it was not till the granting of mineral concessions by the S.A. Republic in 1881 and the formation of mining companies that mines were opened up on the many outcrops of reef. The later mining history of the district is very much that of two large mining companies which were formed in 1895, namely the Transvaal Gold Mining Estates, Ltd. and the Glynn's Lydenburg, Ltd.
:: Geology
It has been generally considered that the mineralized zones containing gold are due to the intrusion of a granite batholith into sediments of the Transvaal System. This theory has been discounted somewhat in recent years. In a number of instances payable zones have been associated with igneous dykes and interbedded sills. It is possible that these dykes and sills were intro the area at much the same time as the Bushveld Igneous Complex some distance to the west. The intrusions created conditions favourable for the percolation of the mineralizing solutions and resulted in the formation of the interbedded reefs and leaders which formed along the planes of weakness. The reefs, for the most part, carry a high percentage of quartz and are oxidized near the surface becoming sulphidic with increased depth of cover.
The rocks of the Transvaal System which form the Drakensberg Escarpment overlie the older granites of the Lowveld. The average dip of the country is 4 to the west. The three separate series of the Transvaal System occur in the area. The following is a brief description of the geological formations of the area indicating the positions of the main gold bearing zones:-
The Pretoria series is the uppermost of the formations and the most important gold carrier is the Columbia Hill shale reef near the base of the Pretoria shales. The reef has been mined fairly extensively at Columbia Hill mine at Pilgrim's Rest and consists of interbedded quartz reefs and a series of vertical quartz leaders in the shales.
The Bevetts reef occuring at the base of the Pretoria shales is strongly formed but has patches of payability scattered over a wide area. The reef has been mined in Pilgrim's Rest at Theta and Iota mines and to the north at Frankfort. The occurence at Frankfort contains a high percentage of sulphides in the non-oxidized zones but owing to its refractory nature has been found difficult metallurgically.
The Dolomite Series varies in thickness from 1000 feet at Sabie in the south to 3000 feet at Vaalhoek in the north. A number of reef horizons occur in the upper beds. The strongest development of these upper reefs is in Pilgrim's Rest with some scattered portions of payability over the entire area.
The Giant Cherts which form the top of the Pretoria series are very prominent un Pilgrim's Rest and are readily recognizable. In places the cherts are mineralized and they have been mined for gold at Theta mine.
The Upper Theta reef lies immediately below the Giant Cherts and is a well-developed honeycombed quartz reef at Theta mine reaching a width of 6 feet with high gold values in some sections.
The Lower Theta reef lies from 50-100 feet below the Upper Theta and is well-developed although narrow in width. It has an average width of 8-14 inches and is a quartz body in the dolomite. The payable areas are mainly oxidized near the surface becoming pyritic under increased cover with lower gold values. The reef has been mined extensively at Theta, Jubilee, Chi, Browns Hill, Peach Tree, Dukes Hill, Clewer and Iota mines at Pilgrim's Rest. It has developed only to a limited extent in the southern area, but has been worked at Frankfort in the north.
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