The Freedmen's Savings Bank

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Monograph

Identifikator:: 175265076X

URN:: urn:nbn:de:zbw-retromon-129631

Document type:: Monograph

Author:: Fleming, Walter Lynwood http://d-nb.info/gnd/120660560X

Title:: The Freedmen's Savings Bank

Place of publication:: Chapel Hill

Publisher:: Univ. of North Carolina Press

Year of publication:: 1927

Scope:: x, 170 S.

Digitisation:: 2021

Collection:: Economics Books

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Chapter

Document type:: Monograph

Structure type:: Chapter

Title:: Chapter VII. The work of the commissioners

Collection:: Economics Books

58 ECONOMIC GEOLOGY Transvaal; the ore is at two horizons in the pre-Palazoic basic rocks of the Bushveld Complex. The lower horizon is a thick band of silicified serpentine which, according to P. A. Wagner and E. T. Mellor, is an altered dunite con- taining a variety of olivine, hortonolite. This dunite occurs in veins and nodules and is traversed by veins of quartz, chalcedonic silica, and magnesite, so that it has been subject to hydrothermal action. A pegmatite—with black horn- blende crystals 3 inches long, and diallage, phlogopite, and magnetite—is associated with the hortonolite-dunite. According to Stanley and Wagner (F. Chem. Soc. S. Afr., xxv, 1G25, pp. 254-9) the platinum is a primary constituent of the dunite; but it frequently occurs as irregular inter- stitial grains that solidified after the other constituents. The upper horizon of platinum is in a diallage-norite that contains pyrite and chalcopyrite, which are presumably secondary. A third platinum occurrence in the Transvaal is in a quartz- lode in the Waterberg Sandstone (pre-Cambrian). This lode has been formed by solutions circulating along a fault, which is post-Karroo and therefore post-Lower Jurassic. Some of the platinum is a replacement after pyrite. The ore has yielded about 24 dwt. to the ton. Platinum has been found in Rhodesia with sulphides in a long dyke-like band of diallage-norite at Makwiro. The rock contains up to 3 dwt. of platinum to the ton, but the particles are said to be so minute that they float on water and cannot be recovered by washing. R. S. Lightbody (Rep. 19, S. Rhod. G.S., 1926) remarks that the presence of the platinum is not easily explained, as it is not in the heaviest of the norite. Brisa CoruMsia—Platinum has been found at Tulameen in the Rocky Mountains of British Columbia in a Jurassic magnetite-olivine-diallagite (koswite), which has been hydro- thermally altered (Poitevin, Canada G.S., Summ. Rep. 1013, pp. 84-101). The koswite surrounds masses of dunite, which also contains platinum. Genesis OF PraTinum OrEs—As chromite, the mineral most often associated with platinum, is an essential con- stituent of dunite, the view has been adopted that platinum is a primary constituent of that rock, and is normally of

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