Devil's Reef, Pigg's Peak, Hhohho Region, Eswatinii

Regional Level Types
Devil's Reef	Reef
Pigg's Peak	Village
Hhohho Region	Region
Eswatini	Country

One of the most spectacular gold occurrences of the supergene type was the Devils Reef gold deposit in neighbouring Swaziland. The occurrence was notable on two counts. Firstly, the ore body although small in size, was exceptionally rich. During 1890-1891, 87,63 kg gold was produced from only 69 tonnes of ore, an average grade of 1,27kg/ton (>0,1% gold). Secondly, Devils Reef is the only deposit documented in the Barberton Mountain Land in which gold occurs in pockets rich in manganese oxides and hydroxides together with large drusy quartz crystals. The quartz crystals reach several centimetres in length and contain a variety of colourful inclusions such as specular hematite, limonite and goethite and red phantom terminations defined by finely disseminated red hematite. The wad also contained rich pockets of gold and many of the surface excavations were located in areas where wad is well developed.

From Hunter (1962):

The Devil's Reef mine is situated on a south-westerly trending ridge to the south of the road from Havelock to Pigg's Peak. The country is deeply dissected and well watered.

The mine workings consist of five quarries, of which four are on the south-eastern flank of the ridge, and adits distributed over seven levels which are at irregular intervals over a vertical distance of 220 feet. The main underground workings are concentrated on No. 6 level on the southeastern
flank of the ridge and on Nos. 2 and 3 levels on the north-western side.

The area around the mine is underlain by sedimentary rocks of the Fig-tree Series and intrusive ultrabasic rocks of the Jamestown Complex. The spine of the ridge is built by cherts of the Fig-tree Series while the south-eastern flank is underlain by talcose schists belonging to the Jamestown Complex. On the north-western side sediments and intrusive ultrabasics are intimately mixed. The strike of the sediments follows the trend of the ridge, the succession dipping steeply south-eastwards.

A banded ironstone horizon about 135 feet thick immediately underlies the main chert which is in turn overlain by quartz-sericite schists which include a narrow band of chert. The banded ironstones are laminated with alternating bands of white chert and reddish brown hematite, varying from t inch to well over an inch in thickness. Lenses and stringers of soft, black ferruginous, manganiferous wad form a stockwork in the banded ironstones. When traced northeastwards along strike, the ironstones grade into banded grey cherts with only poorly developed ferruginous layers at the base.

Two major strike faults disturb the steeply inclined strata, causing displacement and duplication of the banded ironstones and chert, Brecciation is common in the other formations as well. It 'is closely associated with the faulting. Wad is present in the banded ironstones in association with the brecciation. It is soft, black or reddish black and earthy. Specular hematite is disseminated through the wad as foliaceous aggregates or in quartz-lined vugs.

The brecciated zones consist of angular fragments of banded ironstone, chert and talc-schists set in black wad. The fragments are twisted and broken, varying in size from a few inches to several feet. The chert blocks are often powdery and soft. The degree of compaction varies from place to place. The wad and breccia zones decrease in width with depth.

Such gold that has been won from the mine occurs in the wad as isolated pockets of high or very high grade. The breccia is considered to be of mechanical origin due to its association with faults and the presence of talc-schist fragments. The mode of occurrence of the wad and its
association with fresh idiomorphic quartz-crystals suggests that the wad is a secondary introduction subsequent to the brecciation. It suggests that the gold precipitation was associated with the presence of the manganese.

The mine has recently been completely re-sampled and the highest value obtained was 2.61 dwts./ton over 27 inches. Extremely rich, but small, pockets assaying up to 414.95 ounces/ton have been intersected in the past. The investigation failed to reveal any systematic distribution of these rich pockets.

Although the mineral concession was granted as long ago as 1882 and Hall reported in 1918 the existence of the mine, no production figures are available until 1936.

Other Regions, Features and Areas containing this locality

References