Abstract
THE author, in accordance with the requirements of the Ward Fellowship in Economic Geology in Princeton University, spent upwards of four months at Leadville in the study of the ores and their mode of occurrence, and more particularly in. the Morning and Evening Star Mines. The result of his investigations are presented in a very useful memoir dealing with the minuter phenomena of the two mines investigated, which are admirably placed for this purpose, as, although small, they have yielded an enormous quantity of carbonate of lead associated with silver ore in the form of chloride and bromide, the whole deposit being probably a pseudomorph or substitution-pro duct of a blue limestone of Carboniferous age, by infiltration of metallic minerals from an overlying sheet of gray porphyry. This class of substitution is not unknown in other parts of the world, the famous calamine deposit of Vielle Montagne being one of the most familiar examples, but nowhere else is it illustrated on the great scale ob served around Leadville, which now produces nearly one-half of the total quantity of lead raised in the United States. The ore itself varies very considerably in character, consisting of mixtures in every conceivable proportion of hard granular and soft carbonate of lead, often, exceedingly pure, with quartzose brown iron ore and silver chloride and chlorobromide, the latter sometimes in lumps of a few ounces or even a pound weight; more generally, however, it is diffused through the mass, which is enriched to from 50 to too ounces in the ton of ore. A point of great interest, we believe first noticed by the author, is the occurrence of beds of basic ferric sulphate underlying the lead car bonate, and also containing some silver as chloride and lead as sulphate. This the author considers to be due to the oxidation in situ of a belt of iron pyrites more or less mixed with galena, the change being so complete that no trace of pyrites is ever seen in it. In a second section the author gives much interesting detail as to the working of the mines and their produce, the whole forming monograph of considerable value.
The Ores of Leadville, and their Mode of Occurrence, &c.
By Louis D. Ricketts. 4to. (Princeton, New Jersey, 1883.)
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B., H. [Book Reviews]. Nature 29, 571 (1884). https://doi.org/10.1038/029571b0
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DOI: https://doi.org/10.1038/029571b0