A SPECIMEN OF ITACOLUMITE (FLEXIBLE 

 SANDSTONE) FROM SWAZILAND. 



By Prof. G. H. Stanley, A.R.S.M., M.I.M.E. 



The specimen exhibited was found by the writer in July, 

 1907, while on a visit to the property of the Pigg"'s Peak 

 Development Company, Ltd., in Northern Swaziland. 



The district in which the mine is situated is traversed by 

 many parallel bands of quartzites, dipping very steeply, in fact 

 almost vertically, and it was on an outcropping" edge by the 

 side of one of the open workings of the mine that the occur- 

 rence was noted. 



The outward appearance was in no way extraordinary, and 

 it was only by its peculiar " feel " when used as a hand-hold 

 while climbing that the presence of an unusual kind of rock 

 became evident. Closer examination showed that the outcrop 

 consisted of the upturned edges of roughly, perpendicular, 

 parallel sheets of varying thicknesses, worn away to different 

 depths as indicated in Fig. I., the specimen shown l)eing" 



CToie oection 



Fig. I. 



merely a piece broken off from one of the upstanding edges. 

 It will be observed on examination that it exhibits a marked 

 flexibility, and that while its appearance is simply that of an 

 ordinary piece of weathered white sandstone, it is somewhat 

 porous and friable. 



With a view to determining, if possible, the cause of the 

 flexibility, a specimen of the same bed of quartzite was ob- 

 tained from depth in the mine (8th level), and both were then 

 chemically and microscopically examined. 



The chemical analysis shows but little difference, as will be 

 evident on consideration of the following results: — 



Unweathered Weathered 



and alumina (ALO 



Silica (SiO.) 

 Iron oxide (F„03' 

 Lime (CaO) 



Magnesia (MgO) 

 Undetermined 



It will also be evident, however, that nearly all the lime and 

 magnesia of the unweathered specimen, though small in 

 amount, have been dissolved and removed by the weathering, 

 so that it was at first thought to be probable that the crystals 

 of quartz had originally been cemented together by some 

 cementing mineral which had been almost completely removed 

 by exposure, leaving the crystals more or less free and with a 

 certain amount of " play." 



