14 Annals of the South African Museum. 



S 5-26 



P 005 



Ca 0-28 



CI 0-27 



53-59 



If nickel iron (19'49 per cent.), troilite (14-43 per cent.), and 



schreibersite (0-32 per cent.), besides calcium chloride (0-42) and 



oldhamite (0-18) are deducted, the following figures given under 3a, 



or, calculated per hundred, under 36, remain for the silicates soluble 



in hydrochloric acid. 



3a. 



SiO, 9-78 



Al.O. 007 



FeO' 5-85 



MnO 0-33 



CaO 1-33 



MgO 1-45 



18-81 10000 10000 



These figures do not allow of a calculation as an orthosiHcate; even 

 if one wishes to assume that the percentage of ferrous oxide deter- 

 mined by indirect calculation has turned out far too low, the per- 

 centage of silica still remains so high that it can scarcely be explained 

 by this cause alone. A determination of all the silica made as a check 

 resulted in even sevei'al tenths per cent, more (38-71). I am sorry 

 that I must postpone the attempt to find an explanation.''' But if, 

 as from the microscopic examination I must assume, an olivine-like 

 substance is really present, in spite of the large excess of silica, it 

 follows, on the one hand, that this substance diminishes in favour of 

 the enstatite, and, on the other hand, that fayalite and monticellite 

 silicate are strongly represented in it. 



4, Carbon determination. 



The proportion of carbon was ascertained as 0-36 and 038 per 



* In this I have not as yet succeeded. For if the 5-85 FeO, 1-45 MgO, 1-33 CaO, 

 0-33 MnO are reckoned as constituents of olivine, they will require respectively 

 2-44, 1-09, 0-71, 014 of SiO,, making a total of 4-38 of SiO,. Then there would 

 still remain 5-40 SiOi, which could not be taken as quartz since it is the soluble 

 part which is in question. For calculating a felspar the CaO and SiO^ would 

 suffice, but not 0'07 AI2O3. The analysis is not therefore entirely explained, unless 

 the presence of another mineral rich in silica be assumed : but this the microscope 

 did not show. — C. K. 



