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PRODUCED BY FORD and (4) serpentlnlznd limestone (chrysotlle). Of these, the banded Iron stones of South Africa and Western Australia and the alplnc-type ultra, mafic rocks of East Finland are or wore the only major sources of epiphlbole asbestos. v' Anosttc and crocldollte In lronstonee of South Africa The mining of amphlbole asbestos Is now essentially confined to 4 South Africa. The amoslte and crocldollte asbestos occur In the banded Ironstones of the Transvaal Supergroup, a thick succession of Preeambrlan sediments (v 2200 m.y., Trusvell, 1977, p. 42) with vldeepread outcrops In the Transvaal and Cape Provinces and In southeastern Botswana. The two asbestos producing localities are the Tranevaal Asbestos Field In the north-central part of the Transvaal Province and the Cape Asbestos Field In the northern Cape. At present about 200,000 tonnes of amphlbole asbestos are produced yearly from these two fields. Tranevaal Asbestos Field. This field stretches from Chunleepoort easterly to beyond Penge, Transvaal Province, a distance of about 100 to (Fig. 3). Most of the amoslte presently mined is derived from the Penge area, about 80 to north of lydenburg. Minor amounts of amoslte and crocldollte ore mined Intermittently In the Chuniespoort-Mallps Drift orea to the vest of Penge (Dreycr and Robinson, 1978). The Penge ares Is sometimes referred to as the "lydenburg asbestos field" and the Chuniespoort-Mallps Drift area as the "Pietersburg asbestos field." In the Transvaal the rock meuibers of the Transvaal Supergroup con sist essentially of quartrite, shale, dolomite, and conglomerate at the base (Volkberg Formation, Black Reef Series), dolomite, banded Ironstone, ar.d shale In the eenter tone (Dolomite Series); and quartzite, shale and hornfelscs at the top (Pretoria Series). .The asbestos-bearing rocks lie within the Banded Ironstone Stage of the Dolomite Series (Fig. 3). These rocks have been. Intensely folded along two major fold axes (Dreyer and Robinson, 1978), the folding predating the deposition of the Pretoria Scries. The bonding within the ironstones is fine and regular; the *Small amounts of anthophylllte and tremollte asbestos come Into the international market sporadically, at most a few thousand tonnes a year. These types of fiber ore generally from smell, marginally profit able, deposits. 283 8003 0055 Ortf. light colored bands conslse of chert with some slderlte, the dork bands of magnetite end gruncrlte. Within the banded Ironstone sequences the ssbcstos-bearlng seams occupy definite stratigraphic horizons, generally known as the lower Zone, the Main Zone, the Short Fibre Zone, and the Upper Zone. Some Inter icdlnte. zones are developed loeally. Each rone consists of a large number of Individual fiber seems or groups of seams which are given local names (Coetzee et el., 1976). In the Pietersburg asbestos field amoslte and erocldollte are sometimes observed occurring In adjacent seems (Hall, 1930, Fig. 38, p. 212). East of the Mohlapttse River, erocldollte decreases rapidly, so that only amoslte Is found In tt lydenburg asbestos field near Penge. Within the Tranevaal Province there is evidence of thermal metamorphism of the Transvaal Supergroup rocks as a result of the Intrusion of the Bushveld Igneous Complex. For example, the shales of the Pretorlo Series overlying the banded Ironstones were recrystsllizcd to hornfelses, seapollte appears In the dolomites underlying the Ironstones, and amphlbsllutlon took place throughout most of the banded Ironstone sequence. Crystallization of the amphlbole asbestos, however, took place after 239