Reviews — Minerals in Crystalline Limestone. 35 



tlie greiseiiized granite and associated with small veins of quartz and 

 tourmaline in the neighbourhood of its contact with the slates. 

 Lodes of any size are very rare, and tin-ore is never found in the 

 slates themselves. "With the exception of one or two mines, the ore 

 is exclusively won in open works by sluicing the loose alluvial 

 material or the granite in situ, where it has been deeply Aveathered 

 (sometimes as deep as 100 feet) by the efPect of the tropical climate. 

 The mining, except in the case of the Wallaby Creek Company at 

 Rossville, is on a very small scale, and the water power is provided 

 by the local streams, which are led in channels to the site of the 

 workings. As there is a very distinct wet and dry season these 

 streams do not always contain water, so that the raining in some 

 places is confined to the wet season. The Annan Eiver Company, 

 however, are working on a much larger scale, and have erected 

 powerful pumping plant, so that they can rely on a constant supply 

 of water from the lower reaches of the Annan River. This company 

 between 1911 and 1914 raised over 146 tons of tinstone, worth over 

 £17,000, and is the only large producer in the district with the 

 exception of the China Camp group of mines further south, which 

 produced in the same time 269 tons of ore. 



The cassiterite is generally black in colour, but ruby and clear 

 varieties are found in some localities. The only other mineral 

 occurring in quantities which can possibly be regarded as payable is 

 wolfram, of which one or two lodes are known, but this is in very 

 small quantities. 



The field bids fair to continue to produce tin for some long time to 

 come, but will never be a large producer. The content of ore is 

 never very great, being as a rule between 1^ and 2^ lb, to the cubic 

 yard, but exists in great quantities, and is for the most part easily 

 mined. Two factors interfere to some extent with the development 

 of the field, one being the great cost of carriage of materials from 

 Cooktown and the other the scrub-covered character of the country, 

 Avhich makes prospecting very difficult. 



W. H. W. 



X. — Minerals associated with the Crystalline Limestone at 

 Crestmore, Riverside Countit, California. By A. S. Eakle. 

 Bulletin of the Department of Geology, University of California, 

 vol. X, pp. 327-60. Berkeley, 1917. Price 40 cents. 



THIS paper is an interesting contribution to the study of the 

 thermal metamorphism of limestones of varying composition. 

 The limestone forms a mass resting on the upper surface of a mass of 

 igneous rocks and penetrated by dykes. The igneous rocks comprise 

 granodiorite, quartz-monzonite porphyry, and pegmatite. The total 

 number of minerals described is about fifty, and it is clear that these 

 may be divided into three categories, those formed by simple 

 recrystallization of impurities in the limestone, those formed by 

 diffusion into the limestone of material from the igneous magmas, 

 and those belonging properly to the magmas. The limestone is for 

 the most part fairly pure and has crystallized to a white marble. 



