284 THE GEOLOGY OF MINNESOTA. 



[Jordan sandstone. 







At Whalen the St. Lawrence is finely exposed in the bluff that stands 

 in the valley about half a mile below the village. It has here been consid- 

 erably quarried, and furnishes a very good stone for buildings. It lies in 

 even layers which are easily broken into desirable size and shape, furnish- 

 ing a good cut-stone of close grain, without openings. Of the 155 feet that 

 here overlie the St. Croix sandstone, only the lower portion is well exposed. 

 The exposed layers are separated from those seen at the quarry at Clear 

 Grit by an interval of fifty feet. They consist of the following parts, aggre- 

 gating sixty feet. 



Section at Whalen. 



1. Slope, hid by turf (St. Lawrence), 95 feet. 



2. Heavy beds, even-grained, vesicular, the best general building stone, 20 feet. 



3. Bedding confused, not evident, lenticular, - 15 feet. 



4. Fine grit, regular beds, dolomitic, - 20 feet. 



5. Hard, arenaceous, projecting, fossiliferous with the remains of trilobites, 5 feet. 



At Lanesboro the St. Lawrence has" been used in the construction 

 of the principal buildings. The quarries are owned by the Lanesboro Mill 

 Company. The stone presents the usual characters, but has associated 

 masses of marcasite, largely converted to limonite, showing orthorhombic 

 and other forms of crystallization. In s*ome of the cherty nodules are found 

 small orthorhombic crystals of hydrated iron peroxide formed by the con- 

 version of marcasite into limonite. This iron ore is quite plentiful, but 

 seems not to be a native of the rock. It embraces crag and bog-ore depos- 

 its, and is referable to the drift period. (See under drift.) 



The Jordan sandstone. The sandstone lying next above the St. Law- 

 rence limestone, is not so frequently seen along the river bluffs. It is most 

 commonly embraced in that interval of slope that comes between the two 

 lines of limestone outcrop, which is mostly turfed over, as in the bluffs at 

 Lanesboro, and at points between Preston and Lanesboro. Farther down 

 the river, where the strike of the Shakopee runs back from the river a few 

 miles on either side of the valley, it occupies the undulating surface between 

 the immediate river bluffs and the boundary of the Shakopee, as at Rush- 

 ford.* 



In Fillmore county the thickness of the Jordan is not so great as it is 





