Ordovician Sedmients, ' 5^ 



loss of heavier minerals. By this means all slimes were got rid 

 of, as well as a large proportion of the quartz. Concentrates 

 dried, then passed under electro-magnet to separate any mag- 

 netic minerals. The magnetic minerals on examination con- 

 sisted entirely of magnetite. This was also weighed: — 



.9130 grams magnetite through 100-mesh. 



.2889 grams magnetite through 80-mesh and over 100. 



1.2019 grams magnetite total. 



Magnetite in sandstone : .0307 per cent. 



The demagnetised samples were each separated into a lighter 

 and heavier portion, by means of flotation in bromoform S.G.. 

 2.90, on the lines indicated by T. Crook, A.R.C.Sc. (Dublin),. 

 F.G.S., in ''The Petrology of the Sedimentary Rocks," Hatch 

 and Rastall. The concentrates obtained, i.e., the heavier por- 

 tions, were weighed — 



8.301 grams through 100-mesh. 



3.756 grams between 80 and 100-mesh. 



12.057 grams total concentrate. 



These concentrates were seen to be heavily charged with sul- 

 phides, as pyrite and arsenopyrite. They were therefore first 

 roasted to oxide, then again passed under electromagnet to elim- 

 inate pyritic matter, but a good deal of Fe Qs still remained. 

 Hence the only recourse left was to take it into solution with 

 weak Hydrochloric acid, the leached residues being then filtered,, 

 dried and weighed — 



2.7368 grams through 100-mesh. 

 0.4520 grams between 80 and 100-mesh. 



3.1888 grams total. 



Substracting this from the above 12.057 g^rams we find there 

 was a total of 8.868 grams of sulphides in the sandstone, mainly 

 pyrite. 



Sulphide in sandstone — .2730 per cent. 



The acid solution was tested for phosphate, as apatite appeared 

 to be the only likely soluble mineral present. Presence of phos- 

 phate confirmed. 



The filtered residues were noted to contain quite a large amount 

 of quartz, hence at further heavy solution separation was under- 



