STATE GEOLOGIST. Ue 
‘The mineral compositon of typical Ohio clays of this character is 
represented by the following analyses :* 
Clay Substance. Quartz. Held Dye 
NOR a ae ee 53.42 44.41 3.08 
IN@s IAs oo ee} 76.05 19.54 4.28 
The extreme limits of the contents of clay substance are about 40 to 
80 per cent. It is interesting to note the compositions of the clay substance 
which are: 
Per Cents. 
No. 13. | No. 14. 
| 
{SUING SS reroad Beg sane eso Oe i ae ee ee ee Ree 47.70 | 50.19 
Je\ | NUBTONOES ES crate tua casi Solr Rs Reena oe nce ne Rees 33.47 | 32.87 
Rernicro xd CWcemy terres cake rt men ells eet oR 1.96 1.84 
Mi Camichaci layin eases enn bet wae Ue area Rees all Sete eo. ‘Oneal 
JESUS Bs ets A EN oe ta Pon oe Oe I el 0.31 0.16 
WIG VETOVESTIEY oi: ce peg. lal) EEO bra eee aera ae Ee 0.97 1.47 
ANUAINGS. coaic's Wee bata OM ELe woke Oia MEN ae ae eee 4.36 1.82 
Comlbintedswatern ca ec a eh a. | 11.13 | 10.50 
Any of these usually very fine grained clays, with a percentage 
silica-alumina ratio of more than 3, can be ‘made suitable for 
cement purposes by the addition of a little soft iron ore, say 1 to 2 per 
cent. The average percentage silica-alumina ratio is 3.22, while the aver- 
age molecular silica-alumina ratio is 5.47. The latter ratios, being larger, 
are better for pointing out the differences. A molecular ratio of 5.1 might 
be accepted as suitable. But their use should be resorted to only when fer- 
ruginous clays sufficiently high in silica and sufficiently fine of grain are 
not available, owing to the fact that iron oxide lowers the vitrification 
point of cements considerably and hence stands for a lower fuel consump- 
tion. If, however, a manufacturer should be confronted by a choice be- 
tween an irregular ferruginous clay deposit and a bed of silicious second 
grade fire clay, he would do much better to select the refractory clay, 
first, because it is apt to be much more uniform in composition and, second, 
*Langenbeck, Chemistry of Pottery, pp. 67 and £0. Analyses by W. L. Evans, M. Se. 
