GEOLOGICAL FORMATIONS. 679 



the St. Peters, which was exposed in numerous small dry runs. The 

 top of the formation was found to be thirty feet higher on the ridge 

 than at either of the creeks. Although disturbances of this kind are 

 extremely rare and infrequent, yet, in these instances the variations 

 from the normal dip are too plain to be mistaken. 



Ores and Minerals. The St. Peters sandstone has been carefully 

 examined to find, if possible, any indication of openings, either ver- 

 tical or flat, such as exist in the Galena limestone. No evidences 

 were seen, except occasional vertical seams and fissures, which con- 

 tained neither metallic matter, nor minerals and clay, such as are 

 found in veins, and which probably have no connection with the vein 

 system of the Galena limestone. The formation seems to be also per- 

 fectly destitute of organic remains. 



The only indication of metal seen in this formation is the presence 

 of small concretions of sandstone, cemented by a ferruginous sub- 

 stance. This is due to the decomposition of iron pyrites or marcasite, 

 as is proved by its existence in various stages of decay. These con- 

 cretions are not confined to any particular part of the formation, but 

 are much more abundant in the upper beds. They are frequently per- 

 fectly spherical, and, when they occur in the dark-colored sandstone, are 

 often surrounded by a white ring, about half an inch in width, from 

 which the coloring matter seems to have been absorbed. They have 

 been noticed with more or less frequency in various places, but were 

 found most abundantly in the road near the center of Sec 3, T. 1, R. 6 

 E. Another place was observed where the concretions were wanting, 

 and their place had been supplied by a different salt of iron; it was in 

 the S. E. qr. of Sec. 25, T. 1, R. 9 E., at the junction of the Buff lime- 

 stone and St. Peters, The lower bed of the former is full of irregular 

 cavities, and small round holes about one-fourth of an inch in diameter. 

 The upper bed of the sandstone is colored green by some salt of iron, 

 and in it is a seam of greensand and ferruginous matter. It is a pe- 

 culiarity of this formation that the stone hardens on exposure to the 

 weather. In examining any natural exposure, it is found to consist 

 of an outer indurated shell, and an inner and softer sandstone. This 

 is a valuable quality, causing it to be easily quarried and dressed, and 

 enabling it afterward to withstand the influences of the weather. In 

 addition to this, it is easy to find almost any color that may be de- 

 sired. Numerous quarries exist in the vicinity of Mineral Point, 

 furnishing a white and yellowish-red stone, which is extensively used 

 in that locality. 



Situated on Sec. 17, T. 2, R. 4 E., between the villages of Darling- 

 ton and Riverside, on the line of the Mineral Point railroad, is the 



