BUILDING STONES. 393 



establishment of the industry at points remote and the subsequent more 

 ready fulfillment of architectural demands from the quarries Ihst opened- 

 Then- has always been, moreover, a lack of systematic exploration within 

 the Denver Basin, which has also acted as a deterrent. 



The geological horizons of the building stones quarried along the 

 eastern base of the ( !olorado Range are the white quartzites of the Silurian; 

 the Red Beds and Creamy sandstone of the Lower Trias; an occasional bed 

 in the QpperTrias; the Dakota, Fox Hills, and Laramie of the Cretaceous; 

 and the rhyolitic tuff of Castle Lock, of Tertiary age. 



SILURIAN BUILDING STONES. 



The Silurian quartzites lie high on the mountain slopes in the vicinity 

 of Manitou. They are pure white, of remarkably even and fine grain, 

 and extremely hard. They outcrop in a ledge 15 feet thick, traceable for 

 several hundred yards. At present they are but little quarried on account 

 of comparative inaccessibility and excessive hardness, hut they are destined 

 sooner or later to enter in an important degree the list of constructive and 

 ornamental materials of Western cities. No measures of Paleozoic age 

 occur in the 1 >enver Basin. 



TRIASSIC BUILDING STONES. 



The strata of the Trias — the "Red Beds" of the West, the Wyoming 

 formation — yield at various points in Colorado building and other stones 

 of great variety of shade, texture, and strength. East of the range these 

 ocmr ;it a horizon not everywhere the same but usually within 500 feet of 

 the top of the lower division of the formation — a zone which is generally 

 of much liner man-rial and more uniform in texture than the beds lower 

 down. There are three varieties of stone from this general horizon, each 



well adapted to its own special uses: (a) a handsome light-red sandstone, 

 frequently used in superstructures; (b) a hard, banded, comparatively thin- 

 bedded variety, employed as flagging and in foundations on account of its 



greal compressive strength (15,000 pounds to the square inch): and (c) a 

 white quartzite, the homologue of the Creamy sandstone, used extensively 

 west of the Mississippi Liver for curbing, flagging, and paving. 



