THE NONMETALLIC MINERALS. 



179 



by Professor voni Rath, tit a time when the bed was not as fully exposed 

 as it now is, to be at least 1,300,000 tons. 



A curved cut has been made throug-h the sulphur l)ed near the west- 

 ern end, exposing a vertical wall 31 feet high of rich yellow sulphur. 

 The sulphur extends up to the surface over part of the basin, but is 

 mostly covered with sand or rather decomposed andesite. The sur- 

 face of the deposit is wavy, giving the impression of an agitated mass 

 graduallv cooled. The sulphur is partly mixed with sand or gypsum. 

 Most of it is yellow color, while some of it is dark gray, and is called 

 "black sulphur." The deposits of pure sulphur partly resemble the 

 so-called ''virgin rock," which is formed as a product of distillation in 

 the sulphur-flower chambers, particularly when distillation goes on too 

 rapidly. Some also resemble the delicate crystals formed on the walls 

 of such chambers; others are like the crystals formed in slowl}^ cooled 

 masses of sulphur. Gases escape in many places in the cut and in the 

 prospect holes, together with 

 water holding salts in solution. 

 At some points also a consider- 

 ably elevated temperature is 

 observed. 



Of the foreign localities of 

 sulphur, the most noted at 

 present are those of Sicily 

 and Japan. The first-named 

 deposits are descri])ed as occur- 

 ring in Miocene strata involv- 

 ing, from below up. sand}^ 

 marls with beds of salt, limey 

 marls and lignite, gypsum and 

 limestone impregnated with 

 sulphur, black shales, and 

 micaceous sands. Overlying all these is a white, marly Pleocene lime- 

 stone, while below the Miocene is the Eocene nummulitic limestone. 

 The sulphur is found in veinlets and sometimes in larger masses, 

 which ramify through the cellular limestone, as shown in tig. 1 and 

 Specimens Nos. 60932, 60862, 60852, U.S.N.M. 



The yield in sulphur varies from 8 to 25 per cent, rarely running as 

 high as 40 per cent. Below 8 per cent the rock can not be worked. 

 More or less petroleum and bitumen are found in the mines. Barite 

 and celestite sometimes accompanv the sulphur. 



The mining regions are in the southern central portion of the island 

 Girgenti and Larcara are the chief centers. The mines are distributed 

 over an area 160 to 170 kilometers (about 100 miles) from east to west, 

 and 85 to 90 kilometers (55 miles) from north to south. They occur 

 in groups around centers, partly because the sulphur-bearing stratum 



Fig. 1. 



BL(>( K OF LIMESTONE WITH ALTERNATING BANDS OF 

 SULPHUR. 



Sicily, Italy. 



.Specimen No. 60932, U.S.N.M. 



