BUILDING AND ORNAMENTAL STONES. 401 



ley on the Minnesota side, and also at several places farther west, as 

 at Caledonia, in Houston County, Lanesborough and Eushford, in Fill- 

 more County, and at points in Winona County. 



At Stillwater the rock is a silicious dolomite of a light bull' color. 

 In the ledge, which is about 45 feet thick, it occurs in alternate bands 

 of compact and cellular rock varying from 3 to C feet in thickness. 

 The coarser variety is most durable and is used in heavy masonry, as 

 bridges and foundations. The liner variety is used for house trimming, 

 ashlar work, and tombstones. 



At Saint Paul the rock is a fine light-bluish semi-crystalline inagne- 

 sian limestone. It is usually quite regularly stratified, and occurs in 

 beds from 3 to 24 inches in thickness, with joints from 10 to 30 feet 

 apart. Blocks 10 by 5 by 2 feet can be obtained if desired. It is used 

 only locally. At Minneapolis the rock is quite similar, though some- 

 times slightly fossiliferous or mottled with argillaceous spots. It was 

 formerly used almost exclusively in Minneapolis, but is now being 

 gradually replaced by stone from the neighboring States. 



In speaking of these stones Professor Winchell says :* 



u In the use of the Trenton limestone quarried at Saint Paul and 

 Minneapolis regard should be had constantly to its laminated structure. 

 The beds quarried now are as they were originally deposited, and as 

 cut for use embrace in every block many layers of from one-half to two 

 inches in thickness. These consist of alternating clayey and calcareous 

 portions, the latter constituting the hard and enduring part of the stone. 

 These layers are not always distinct and continuous over large surfaces, 

 but they blend or shade into each other every few inches. Yet in process 

 of time, under natural weathering, they get separated so as to fall apart, 

 the clayey matter disintegrating first and causing the calcareous struct- 

 ure which sustains the whole to bre^ak up into small sheets or fragments. 

 Hence this stone should never be placed on edge, but in the same 

 position it occupied in the quarry. It should never be allowed to oc- 

 cupy projecting or exposed parts of a building. More especially if it 

 be on edge and in a projecting cornice or capital it is the source of 

 weakness to the structure, as well as of danger to all passers, from the 

 dropping of sheets or fragments as the weather, by wet or frost, sepa- 

 rates them from each other. Its color is also against its being put in 

 the exposed and ornamental parts of a structure. * * * The color 

 of the Trenton makes it very suitable for foundations and for the 

 ranges below the water-table, but even there it should be well bedded 

 in mortar and protected by the water-table in order to keep out the 

 water.' 7 



At Red Wing, in Goodhue County, the stone is quarried only for 

 local building and for burning into quicklime. Blocks as large as can 

 conveniently be handled can be obtained. At Frontenac, in the same 

 county, the stone is of a buff or gray color, medium fine, and quite 



* Preliminary Ren. on Building Stone, etc., 1889, p. 33. 



H. Mis. 170, pt. 2 -26 



