Lehre von den Erzlagerstätten

Abstract

WE are thankful to find that Dr. Beck has not kept us waiting an unduly long time for the concluding portion of his valuable work, the first instalment of which was recently reviewed in these pages (see p. 2 45 January 10). The first part brought the description of the different classes of mineral deposits nearly up to the end of Fissure Veins; this subject is now brought to a conclusion with a number of general observations on this important group of ore deposits, the only criticism upon which need be that their limitations are somewhat too narrowly drawn. Most of the phenomena here described, such as the formation of gossans, enrichment or impoverishment of ores in depth, effects upon the surrounding “country,” &c., are by no means confined to fissure veins, but are common to all classes of mineral deposits, depending as they do essentially upon the chemical composition of the mineral contents of the deposit, and either not at all or only in very remote degree upon its genetic relations or morphological features. The alterations and oscillations of mineral constitution that many veins show in depth are well but briefly described, although, perhaps, their close connection in many cases with changes in the country rock is hardly enough insisted on. It is almost certain that the well-known change in depth in the silver and copper contents of the Montana copper deposits is purely a secondary phenomenon, and Dr. Beck is most probably in error when he ranks this among the primary modifications of ore deposits. The description of secondary alterations of deposits and the formation of gossans is extremely good, the chemical investigation of the subject being especially convincing. It must be noted that Dr. Beck only refers under this head to secondary changes above the permanent water-level (in the region of Posepny's vadose circulation) and not to the phenomena which have recently attracted so much attention in America, and which, under the head of Secondary Enrichment of Ore Deposits, have been so ably investigated by Emmons, Weed and others; these Dr. Beck appears to omit entirely.

Lehre von den Erzlagerstätten.

By Dr. Richard Beck. ii Theil. Pp. ix–xviii + 385–724. (Berlin: Borntraeger, 1901). Mk. 8.50.