420 REPORT OF NATIONAL MUSEUM, J899. 



stones in Hungary. No deposits of such extent as to be of economic 

 importance are known within the limits of the United States. Alunite 

 as an alteration product of rhyolite has been described by Whitman 

 Cross 1 as occurring at the Rosita Hills in Colorado, the alteration being 

 brought about through the influence of sulphurous vapors incident to 

 the volcanic outbursts. The altered rhyolite as shown by analyses had 

 the following composition: Silica 65.94 per cent; alumina 12.95 per 

 cent; potash 2.32 per cent; soda 1.19 per cent; sulphur trioxide 12.47 

 percent; water 4. 47 per cent; Fe 2 O 3 , etc., 0.55 per cent. This indicates 

 that the rock is made up of alunite and quartz, in the proportion of 

 about one-third of the former to two-thirds of the latter. The most 

 noted occurrences of alunite are at Tolfa, near Rome; Montioni, in 

 Tuscany, Italy (Specimen No. 62863, U.S.N.M.); Musaz, in Hungary 

 (Specimens Nos. 60925, 66854, U.S.N.M.) on the islands of Milo, 

 Argentiera and Nevis in the Grecian Archipelago; Mount Dore in 

 France, and at Bulledelah in New South Wales. At the last-named 

 locality the mineral occurs in compact, micro-crystalline forms of a 

 slight flesh pink tint, in "a large deposit forming the summit of a 

 ridge about three-fourths mile long by one-half mile wide, and rising 

 about 1,000 feet above the level of Lyall Creek, on which it is situ- 

 ated. Viewed from the creek it presents a massive outcrop re- 

 sembling limestone. It yields from 60 to 80 per cent of alum upon 

 roasting, lixiviating, and evaporating 2 (Specimen No. 62179, U.S.N.M.). 

 Alunite from the mines at Tolfa varies considerably in composition. 

 The crystallized variety contains about 32 per cent alumina, whereas 

 the cruder specimens which contain a large quantity of silica have 

 only about 17.5 per cent. The following is an analysis of an average 

 sample: 



Alumina 27. 60 



Sulphuric acid 29. 74 



Potash 7. 55 



Water 11. 20 



Iron 1. 20 



Silica .... . 22. 71 



Total 100. 00 



W T hen crushed it is easily reduced to a powder, the finer portions of 

 which are richer in alumina than the coarser portions, and for this 

 reason the author recommends that only the former should be exported, 

 the latter being converted into commercial products in the vicinity of 

 the mine. 8 



1 American Journal of Science, XLI, 1891, p. 468. 



2 Catalogue of New South Wales Exhibits, World's Columbian Exposition, Chicago, 

 1893, Dept. E, p. 358. 



3 Journal of the Society of Chemical Industry, I, 1882, p. 501. 



