198 
CEMENT MATERIALS AND INDUSTRY. 
[bull. 24 
SHALES AND CLAYS. 
Surface clays as well as shales from the Traverse and Coldwate 
formations have been used in Portland-cement plants in Michigan. I 
addition, shales from the Antrim and Saginaw formations may furnis 
supplies in the future. 
The following descriptions of shales and clays are taken from Ruii 
sell's report: 
The shale of the Traverse group is utilized by the Alpena Portland Cement Con 
pany in connection with limestone from the same formation, and is obtained froi 
quarries about 7 miles north of Alpena and near the shore of Lake Huron. Tr 
strata are nearly horizontal and consist of alternating layers of fine-grained and un 
form bluish-black shale alternating with thin-bedded impure limestone. At tr. 
locality where the quarries are located the shale occurs at the surface, being covere 
only by 2 or 3 feet of peat. The same bed is understood to occur in the low blu 
bordering the neighboring portion of Lake Huron. The surface portion of the sha 
where now exposed is disintegrated to a depth of a few inches, so as to form a stii 
blue clay, and both the surface material and the unweathered shale beneath ai 
suitable for cement making. The general composition of the shale is indicated t 
the following analyses: 
Analyses of shale of the Traverse group from near Alpena.® 
[Analysts, A. N. Clark (A) and H. Ries (B).] 
Constituent. 
Silica (Si0 2 ) 
Alumina ( A1 2 3 ) 
Ferric oxide (Fe 2 3 ; all iron computed as Fe 2 3 ' 
Calcium carbonate ( CaC0 3 ) 
Magnesium carbonate (MgC0 3 ) 
Alkalies, as K 2 
Water, organic matter and difference 
55. 95 
17.43 
7.67 
2.14 
1. 55 
2.86 
12.40 
Total 
Ferrous iron ( FeO) 
100. 00 
.50 
58. (.1 
I7.( 
11.1 
100. 
Another analysis of shale from the same locality as the above, supplied by tl 
Alpena Portland Cement Company, is as follows: 
Analysis of shale of the Traverse group from near Alpena. 
[Analyst, S. H. Ludlow.] 
Silica (Si0 2 ) 57.1 
Alumina (A1 2 3 ) 20. f J 
Ferric oxide (Fe 2 3 ) ,. 3. ( 1 
Calcium carbonate ( CaC0 3 ) ., 9. : 1 
Calci um oxide ( CaO ) 1 ] 
Magnesium carbonate (MgC0 3 ) 5. < J 
Sulphuric anhydride (S0 3 ) ' : 
Alkalies (Na 2 and K 2 0) 3. < .] 
Total 99.1 
aGeol. Survey Michigan, vol. 8, pt. 1, p. 16. 
