346 THE GEOLOGY OF MINNESOTA. 



[Brick. Gold. 



deposits from two to ten or twelve feet thick. Although this material is 

 sandy, more sand is usually put in in making the brick. The brick are con- 

 sequently tender and of poor quality. They vitrify but little when burned. 



Gold has been found in the drift along the Zumbro from Rochester and 

 Oronoco down to the Wabasha border and beyond. It is found only on the 

 Cambrian limestones. Murchison calls attention to this fact as generally 

 true. It is found in the drift about the stream, but mostly in the bed of 

 the stream, or in material worked over by it at a comparatively recent 

 date. In the same alluvial material is found a small amount of black mag- 

 netic sand, of a specific gravity approaching that of gold. When the gold 

 is obtained by washing, after all the other materials are washed away this 

 heavy black sand remains, and the minute fragments of gold are picked out 

 from it. It is therefore here called the "mother of gold," and the two are 

 thought to be always together, a conclusion which need not necesarily 

 follow. 



The gold is in minute, angular fragments. The quantity is so small 

 that it does not pay to work it by the ordinary method of hand-washing. 

 Washing on a more extensive scale might be made to pay. It has been 

 tried two or three times, but never under favorable circumstances, or for 

 periods of much length. 



It may be worth while just here to call attention to the fact that gold 

 is frequently found under these circumstances. It has been found over ex- 

 tensive regions in Canada where attempts at obtaining it on a large scale 

 have always failed to pay. It occurs thus in Vermont, Ohio, Indiana. Wis- 

 consin, Iowa, and has been reported in other counties in Minnesota, viz. : 

 Fillmore, Wabasha and Scott. 



