eckel.] MICHIGAN. 199 
The region in the northern portion of the southern peninsula in which shales of 
the Traverse group may outcrop on the borders of lakes or along streams, or may 
be discovered by making small excavations, is indicated on the map. 
COLD WATER SHALES. 
The Cold water shales are now being quarried at a locality about 1 J miles east of 
Union City and utilized by the Peerless Portland Cement Company. At the quarry 
referred to the shales are well exposed to a depth of from 20 to 35 feet, are thin 
bedded, horizontal, and contain irregular concretions of ferrous carbonate, some of 
which are charged with fossil marine shells. The rocks near the surface are much 
weathered and so completely disintegrated that the evenly bedded bluish shales below 
pass upward into yellowish mottled clays near the surface. In the manufacture of 
Portland cement an approximately equal mixture of the weathered and unweathered 
material is now used. The range in percentage of the several constituents compos- 
ing the shale is as follows: 
Analyses of Coldwater shale from near Union City. 
[Analyst, A. Lundteigen.] 
Silica (Si0 2 ) 67. 89 to 59. 20 
Iron and aluminum oxides (Fe 2 3 and A1 2 ;5 ) 29. 89 to 23. 33 
Calcium (CaO) 1. 42 to .00 
Magnesium (MgO) 2. 16 to .26 
Sulphuric anhydride ( S0 3 ) Trace to . 00 
Alkalies, by difference 8. 55 to 6. 00 
Moisture, including water of composition 20. 50 to 10. 00 
The Coldwater shales are also used at the works of the Michigan Portland Cement 
Company, near Coldwater, and there present about the same characteristics as at 
Union City. Their range in composition is as follows: 
Analyses of Coldwater shale from near Coldwater. 
[Analyst, H. E. Brown.] 
Silica (Si0 2 ) 57. 26 to 61. 25 
Alumina ( Al 2 O s ) 18. 12 to 21 . 59 
Ferric oxide (Fe 2 O s ) 6. 53 to 8. 30 
Calcium (CaO) 1. 25 to 1. 50 
Magnesium (MgO) . 1. 49 to 2. 31 
Sulphuric anhydride (SO s ) 65 to 1. 34 
Carbon dioxide (00, ) 95 to 1.18 
Titanium oxide (Ti0 2 ) 82 to 1. 12 
Alkalies (Na 2 and K 2 0) 2. 25 to 3. 45 
Loss on ignition , 6. 19 to 8. 32 
The shales of this formation were formerly used by the Bronson Portland Cement 
Company, but have been superseded by surface clays obtained in northern Ohio. 
The shale formerly used at Bronson is reported to have the following composition: 
Analysis of Cold water shale from near Bronson/ 1 
[Analyst, C.J. Wheeler. J 
Silica ( Si0 2 ) ' 62. 00 
Alumina ( A1 2 3 ) - 20 - 00 
Ferric oxide (Fe 2 ;i ) 8. 00 
Calcium (CaO) . . .'. !. 50 
Manesium (MgO) 1. 00 
Sulphuric anhydride (S0 3 ) 50 
Organic matter 8. 00 
Total 100. 00 
«The plant of the Bronson Portland Cement Company, Bronson, Mich., by H. Lewis: Eng. Rec, 
vol. 37, 1898, pp. 470-472; reprinted in The Cement Industry, New York, 1900, pp. 33-44. 
