88 
Myr. E. T. Harpman—On the Chemical Composition of Chert. 
Awnatysis V. 
ae 
SiO, (insoluble), 8 a 
Si0, (soluble) x by 
A1,0,, : 6 1:50 
Fe,O , 2 = 
FeO, 0:50 
CaO, a 
MgO, — 
CaCO,, 25-40 
MgCoO,, : 0:50 
Organic matter, water, and sulphur, . 3.50 
Insoluble residue: ; 68-28 
99°68 
Specific gravity, 2-626. 
Such specimens might be termed pseudo-cherts. 
No. 9. A dark highly siliceous limestone. 
Total 
Analysis, 
65°15 
traces 
3:55 
0:45 
0:50 
0:95 
trace 
25-40 
0:50 
3:50 
100-00 
Although to all appearance a true chert in outward character, the analysis shows 
this to be strictly a very calcareous chert. It is clearly in the transition state. 
Hard and extremely tough ; scratches 
easily, and effervesces freely. It passes in places into true chert, a few strings of 
which are visible. 
sulphuretted hydrogen on being crushed. 
ANALYSIS VI. 
a, 
Si0, (insoluble), ° : - 
Si0, Coa . : 5 traces 
Fe, 0, ; 5 jf - 
Al, Los t 6 : t 0:50 
FeO, ¥ 3 : . 0:35 
CaO, 4 : 6 6 - 
MgO, , : : — 
CaCO,, ; , : 73°22 
MgCoO,, WPA 5) 
Water 1-00, org. mates 1:48, aad sulph. 2°30, 4:78 
Insoluble residue, 3 4 18:60 
100-20 
Specific gravity, 2-647. 
No. 10. White chert passing into light gray siliceous limestone ; 
Like Nos. 5 and 7, this specimen gives off a strong odour of 
Total 
Analysis. 
16-00 
traces 
trace 
1:20 
1:10 
1:50 
trace 
13:22 
2-75 
4°78 
a) 
100:55 
extremely hard 
and brittle, being much jointed. Cannot be scratched; effervesces but slightly. 
This specimen exhibits incipient rhombohedral cleavage, modified by the peculiar 
splintery fracture of chert. 
