lis Trenton Linicsfone of Minneapolis and St. Paul — Halt. 



Comparisons With Other Quarries. — But little time can 

 be taken here in comparing this quarry in its general relations 

 with others in the neighborhood. The broader characters of this 

 spot can be seen almost everywhere that bmestone is broken with- 

 in the two cities. At the Maloney quarry, a mile below this one, 

 and on the same side of the river, the beds appear to be more 

 compact; the upper layer is less ^ha\y and yields some stone for 

 rubble work, while the building stone layer contains fewer of 

 those argillaceous bands which are so deleterious. At Saint Paul the 

 building stone layer is somewhat thicker than here, but on the 

 whole it yields no perceptibly better stone. The belt of green 

 j^hale which occurs at Finns Glen and in South Saint Paul con- 

 tains numerous slabs of lenticular shape andsmall area, which seem 

 to be entirely made up of fossils.* In composition they must 

 be very pure calcium carbonate, while the shale itself cannot con- 

 tain more than 60 percent, or 70 per cent, of thac material. 



In Northeast Minneapolis, on the other hand, the quarries lie 

 nearly on the northern boarder of the Trenton area of the state. 

 All the layers are badly stained and loosened by the action of 

 water carrying solvents and staining mixtures, especially hydrous 

 ferric oxide. In some quarries where the central portions of the 

 layers are quite fresh and blue, the rock next the vertical joints 

 and the bedding joints is stained to the depth of an inch or so with 

 a light brown limonite stain, either brought down from the over- 

 lying drift material or obtained by the oxidation of a ferrous oxide 

 in the loek itself. 



Thk Jjithological Characters of the Trentox. — These 

 characters harmonize closely with the structural and stratigraphi- 

 cal details already outlined. The building stone layer contains, 

 in some of its bands tolerably pure calcium carbonate. It does 

 display, however, an occasional minute pyritous mass or a granule 

 of carbonaceous matter. But as a rule under the microscope almost 

 the whole field is made up of rhombohedrons of calcite or dolomite, 

 and these forms are very perfect, excepting only when they are de- 

 veloped from nuclei so near together that contact soon interrupts 

 their growth. One fact noted in all the slides examined, was the 

 scarcity of twinned forms. Were it not for the results of the chemi- 



*Theso fossils eousist of several species of orthis, rhynchoaella, stroph- 

 omena, etc., Init the largest proportion is made u]) of many species of bryo- 

 /oa and, j)rol)al)]y. several spon«>es. 



