4o8 E. C. HARDER AND R. T. CHAMBERLIN 



Nearly all the early workings were shallow open cuts or shafts, 

 or short tunnels. Later development led to the operation of a few 

 deep mines, such as the Descoberto mine near Sahara, the Gongo 

 Socco and Sao Bento mines between Caethe and Santa Barbara, 

 the Pary mine near Sao Francisco, and the Santa Anna and Maquine 

 mines near Marianna. The shallow workings cover large areas and 

 are widely distributed in central Minas, groups of them being found 

 in the vicinity of nearly all the small towns and villages, for in most 

 cases it was the gold mines that caused the founding of the villages. 

 Some of the areas of old abandoned workings cover many hundreds 

 of acres. 



Gold occurs in Minas Geraes in three different associations: 

 (i) in quartz or sulphide veins, (2) disseminated in the iron forma- 

 tion and in the canga derived from it, and (3) in stream gravels. 



Gold-bearing quartz veins occur with different relations; some 

 of them are strike veins, others occur along bedding or schistosity 

 planes; some are long and continuous, others short and lens-like. 

 In some places groups of short parallel or intersecting veins are 

 found, while elsewhere single isolated veins of considerable extent 

 occur. 



Quartz or sulphide veins containing gold may occur in the base- 

 ment complex or in any of the sedimentary formations. The 

 Morro Velho mine at Villa Nova de Lima is operating a large vein 

 in the Piracicaba schist on which they have descended for a 

 vertical distance of more than 1,700 meters, deeper than any other 

 gold mine in the world. The Passagem mine near Ouro Pre to is 

 working on an irregular bedding vein impregnating a thin layer of 

 Batatal schist between the Caraja quartzite and the Itabira iron 

 formation. In the old workings near Ouro Preto quartz veins are 

 found cutting the Caraga quartzite and the Itabira iron formation. 

 Near Cattas Altas old workings are found in the basement complex 

 and here also quartz veins occur. Many other examples might be 

 given of quartz veins found in the various formations. 



The mineral veins of the district for the most part come under 

 two general heads: (i) ordinary quartz veins, and (2) veins of 

 magmatic origin. To the first class belong certain quartz-hematite 

 veins occurring in the iron formation, and the numerous barren 



