u8 SCIENCE PROGRESS 



i. The Mount Lyell Copper-Field 



The Mount Lyell district illustrates Australian mining at 

 its best and at its worst. It is littered with costly failures, 

 owing to a wrong idea as to the geological structure of the 

 field ; and its richest high-grade mine has been harassed by a 

 succession of the mistakes that are probably inevitable, when 

 a distant management attempts the development of a new and 

 exceptional mining-field. The mass of ore known as the " Iron 

 Blow" was discovered at Mount Lyell in 1883, and it was 

 believed by eager speculators to be one outcrop of a lode, 

 which would have a length and uniformity, equivalent to its width 

 and purity at the place exposed. Streaks of ore running through 

 the adjacent country rocks strengthened this belief; and so the 

 mining-field was pegged out among over thirty companies, of 

 which only three have ever paid a dividend, and only one can 

 yet be regarded as an established success. The one company 

 has, however, saved the reputation of the field. It has suc- 

 ceeded in the profitable working of an especially difficult low- 

 grade ore by a combination of sound business management, 

 expert scientific skill, and brilliant originality in mining methods. 

 At the invitation of the Mount Lyell Company I had the oppor- 

 tunity to study this field and inspect all the mines then under 

 its control. The results of that study have been stated in a book 

 published by the Australian Institute of Mining Engineers, 

 describing the geology of the field and giving a new explanation 

 of the genesis of its ore. 1 



The ores of the Mount Lyell field consist of a series of 

 isolated masses of sulphides, including copper pyrites, gold, and 

 silver. The most famous of the deposits, the " Parent Mine " of 

 the field, is a vast mass of pyrites, 800 ft. long and 200 ft. broad. 

 Mining work and bores have shown that the mass first tapers 

 and then ends abruptly below. The main mass of ore is 

 pyrites ; but on the hanging-wall side is a wedge-shaped block 

 of hematite, known as the " Iron Blow." This mass of iron 

 oxide contained some 15 oz. per ton of silver and 15 dwt. per 

 ton of gold. Mining was begun on the Iron Blow, its ore being 

 crushed in order to obtain the gold by ordinary milling. This 



1 J. W. Gregory, The Mount Lyell Mining-Field* Tasmania; with some 

 account of the geology of other pyritic ore bodies, Melbourne, 1905, viii + 172 pp., 

 16 plates and maps. A Bibliography is given on pp. 164-8. 



