268 JOSEPH STRUTHERS 



from 1 to 7 per cent of silica. French bauxite is used chiefly 

 in the manufacture of alum and alumina — the white variety, 

 containing but litt le iron oxide, for alum ; and the red variety, 

 containing but little silica, after purification, for alumina. 

 Because of the low cost of mining and the low ocean freights of 

 recent years, large quantities of this mineral have been brought 

 to the United States and consiuned, mainl}- for the manu- 

 facture of alumina from which metallic aluminum has been 

 made. At the present time there is little, if any, French 

 bauxite used for the manufacture of aluminum sulphate. 



In the United Kingdom there are important deposits 

 at Strain, near Ballj^clare, and at Glenravel, both in county 

 Antrim, Ireland. Of the European deposits, these are next 

 in importance to those of France. An extensive use of this 

 mineral of county Antrim for the manufacture of aluminum 

 has been retarded, because the high percentage of silica it 

 contains renders it inferior for this purpose to the bauxite 

 of France. It is, however, of excellent quality, and contains 

 but little iron oxide or titanic oxide. Much of the product 

 of the Irish mines is consumed in England, where it is made 

 into alum. 



In Germany there are several deposits of bauxite of 

 considerable extent, but the quality is inferior to that of the 

 French mineral. In one locality, however, the mineral is 

 quite pure, but the deposit is too small in extent to be com- 

 mercially valuable. 



Austria, Italy, Asia Minor, French Guiana, and New 

 South Wales also possess deposits of the mineral, but as yet 

 none has been developed to the productive stage. 



The mineral bauxite is a hydrated aluminum oxide con- 

 taining also various quantities of ironoxide (FejOs) and silica 

 (SiOs). Three varieties are distinguished, the monoh3^drate 

 (AlA^HoO), the dihydrate (AL03,2HoO), and the trihydrate 

 (AlsOsjSHsO). Apart from impurities the composition of these 

 minerals varies from the monohydrate (diaspore), which 

 contains 85.12 per cent of AI2O3 and 14.88 per ccTit of H2O, to 

 the trihydrate (gibbsite), which contains 65.61 per cent of 

 AI0O3 and 34.39 per cent of H2O. More or less of the alumina 

 in bauxite is replaced by iron or manganese oxides. Silica 



