Mr. E. T, Harpman—On the Chemical Composition of Chert 89. 
Ayatysis. VII. 
Total 
Analysis, 
SiO, (insoluble), : 5 é = 93208 293!20 
SiO, (soluble), in HCl, 3 . trace - trace 
Fe,0,, . . . 
AvoR \ : : 1-15 0-80 1-95 
FeO, : 5 : : 0:10 = 0:10 
CaO, : y : : - 0:70 0:70 
MgO, 6 - ; : - trace trace 
CaCO,, : 6 i ; 2-90 - 2°90 
MegCoO,, : ‘ ; 6 0:20 = 0:20 
Water and loss, = 4 9 0:95 - 0:95 
Insoluble residue, . : 9 94°65 = = 
99-45 94-70 100-00 
Si0,, soluble in caustic potash, 0°45 per cent. 
Specific gravity, 2°750. 
In the analysis of this specimen a curious circumstance was noticed. The fused 
mass dissolved readily in water, but the addition of hydrochloric acid failed to 
precipitate the silica in the gelatinous, condition as is usual. The liquid remaining 
perfectly clear until evaporated almost to dryness. The same occurred with No. 
15 (see post). 
No. 11. An extremely hard black chert, cannot be scratched, effervesces but 
very slightly with acid; incipient rhombohedral cleavage like the last, so that it is 
rather easily broken up, the cleavage planes are coated with more recent cale-spar ; 
but the portions taken for analysis were carefully selected, so as to be free from 
this. 
Anatysis VITT. 
a ie Total 
Analysis, 
SiO, (insoluble), ; : ; - 93:10 93:10 
S10, (soluble) ; A 5 trace = trace 
Fe,O, : 2 , : 
Mtoe ; ; t : 0-40 0:50 0:90 
FeS, ¢ 0 : 5 trace - trace 
CaO, 5 ; : : 0°30 0:30 
MgO, 6 . : : - trace trace 
CaCoO,, 5 0 : 5 3°75 = 3.75 
MgCoO,, ‘ : 5 : trace - = 
Water and organic matter, &c., : 1-95 = 1:95 
Insoluble residue, : ; 5 93-90 = = 
100-00 93-90 100-00 
Specific gravity, 2-652. 
No. 12. Bedded chert. Dark, compact, extremely hard chert—impossible to 
scratch—hardly any effervescence with acid even when powdered. Tested accord- 
ing to Plattner’s and Von Kobell’s methods, gives evident traces of the presence 
of a metallic sulphide, doubtless iron-pyrites, which Mr. Hull has observed in the 
microscopic section. 
Q 2 
