BUILDING STONES. 151 



Red Quartzyte.] 



the south. This range of quaitzyte, being the only rock found accessible 

 throughout a wide extent in that part of the state, will be more largely 

 quarried as the country becomes settled more thickly, and as buildings of 

 more substantial character come to be required in the larger towns. 



In Rock county are numerous exposures of the same red qnartzyte,* 

 the principal one, known as The Mound, being west of the Rock river, near 

 Luverne. This mound is caused by the breaking off, nearly perpendicularly, 

 of the strata of an extensive high plateau running northwest from there, 

 consisting of this rock. The elevation is 175 feet above the river. The 

 perpendicular bluff of rock rises from forty to sixty feet in its highest part, 

 but owing to a dip of about twenty degrees from the horizon toward the 

 west, or partly northwest, and to the breaking off of the upper layers, caus- 

 ing a gradual ascent from the brow of the hill backward through several 

 rods, the actual thickness of beds visible may be 150 feet. The rock here 

 appears to be almost entirely a reddish, or pink, heavy-bedded quartzyte. 

 If wrought there might be some softer and thinner layers discovered, and 

 such probably exist in the lower parts of the bluff, now hid by the copious 

 talus of refractory and large blocks fallen from the hard layers above. The 

 main bluff curves westwardly at both ends, and by reason of the dip and 

 ravines that enter the valley from the west, its exposed layers gradually 

 disappear under the soil in that direction, but evidently are the cause of the 

 range of elevated land running northwestwardly, since they are seen in 

 numerous other places. 



The principal locality in Pipestoue county is at the famous quarry 

 of the Indians near Pipestone City, which, however, was worked by them 

 for the layer of metamorphosed red clay which is embraced between the 

 quartzyte strata. There has been but little quarrying done at this place, 

 the greater part of it having been executed by the Indians. There is a 

 ledge of rock which runs north and south nearly three miles, consisting of 

 layers of red quartzyte with a gentle dip toward the east, forming a per- 

 pendicular escarpment toward the west, and rising at its highest point not 

 more than twenty-five feet above the level of the prairie on the west. The 

 rock here in general is exceedingly hard, in heavy layers one to three feet 

 thick, separated by jointage planes into huge blocks of angular shapes, that 



*Compare the .sixth annual report. 



