102 



AQUEOUS EOCKS 



was derived by leaching, being transported in the form of 

 soluble salts and finally precipitated as oxide or carbonate, the 

 latter being subsequently converted into oxide. The deposits 

 occur as a rule in residual clays, as interbedded strata in shales 

 and sandstones, or as occupying superficial seams and joints, 

 and in the form of pockets and nests. True fissure veins of man- 

 ganese oxide are not known. 



Beauxite (so called from Beaux, near Aries, France) is the 

 name given to a somewhat indefinite mixture of alumina and 

 iron oxides, occurring in the form of compact concretionary 

 grains of a dull red, brown, or nearly white color, and also 

 in compact and earthy forms. The mode of occurrence of the 

 mineral is somewhat variable. At Beaux and several other 

 localities it occurs in pockets in limestone, and also in beds 

 alternating with limestones, sandstones, and clays belonging 

 to the Cretaceous period. In the Puy-de-D6me the beds rest 

 directly upon gneiss, and are overlaid by basalt. At Oberhes- 

 sen, Germany, the mineral occurs in rounded masses embedded 

 in clay, as is also the case at Vogelsberg. In America, beaux- 

 ite has been found in Alabama, Georgia, and Arkansas. In 

 Alabama and Georgia it occurs in beds of irregular extent, 

 associated with limestones of Upper Cambrian age (the Knox 

 dolomite) ; in Arkansas the deposits are of Tertiary age. 



The origin of the beauxite is somewhat obscure. It has been 

 argued that the beds at Beaux, and those of Var, are deposits 

 from mineral springs. Those of the Puy-de-D6me, the West- 

 erwald, Vogelsberg, and of Ireland, on the other hand, are 

 regarded as derived from basalt by a metasomatic process. 



Chemical Composition op Beauxite 





CONSTITITENTS 



I 



11 



III 



IV 



Y 



Silica (SiOg) 



Alumina (AI2O3) . . .' 

 Iron sesquioxide (Fe203) . 



Water (H2O) 



Titanium oxide (Ti02) • 



2.8 0/, 

 57.6 

 26.3 

 10.08 



3.1 



1.10% 

 60.92 

 15.70 

 27.76 



3.20 



21.08 % 

 48.92 



2.14 

 23.41 



2.62 



2.80% 

 62.21 

 13.60 



27.72 

 3.62 



10.38 % 

 65.64 



1.96 

 27.62 



3.60 



I. Beaux, Pranee. II. Vogelsberg, G-ermany. III. tlacksonville, Alabama. 

 lY, Floyd County, Georgia. V. Pulaski County, Arkansas. 



