PUZZOLANIC MATERIALS IN GENERAL. 



TABLE 236. 

 ANALYSES OF POZZUOLANA FROM THE AZORES ISLANDS. 



635 



1. From St. Miguel. tetin. Zervas, analyst. School of Mines Quarterly, vol. 18, p. 230. 



2. pozzuolana. Chateau, 



3. Terceira. Zervas, " 



Volcanic materials of a type somewhat different from normal pozzuo- 

 lana occur on Pile Bourbon, a French island lying about 400 miles east 

 of Madagascar. 



ANALYSIS OP VOLCANIC ASH, ILE BOURBON. 



Silica (SiO 2 ) 25.67 



Alumina (A1 2 O 3 ) 16.33 



Iron oxide (Fe 2 O 3 ) 40 .00 



Magnesia (MgO) tr. 



Water (H 2 O) 17.00 



Trass. Trass is a pale yellowish to grayish rock, rough to the feel, 

 composed of an earthy or compact pumiceous dust mixed with fragments 

 of pumice, trachyte, carbonized wood, etc. It is, so far as origin is 

 concerned, an ancient volcanic mud. Trass occurs along the Rhine, 

 in Rhenish Prussia, from Koln on the north to Coblenz on the south. 

 The towns of Brohl, Kruft, Plaidt, and Andernach, all located north- 

 west of Coblenz and within fifteen miles of that city, are prominent 

 points in connection with the trass industry. A series of analyses of 

 trass and related products is given in Table 237. 



Santorin. The island of Santorin, or Thera, is one of the most 

 southeasterly of the islets of the Grecian Archipelago, lying in the 

 Cyclades group. An ash called in commerce "santorin ", derived from 

 the volcano of the same name, is quite extensively shipped for use 

 as a cementing material. 



