562 REPORT OF NATIONAL MUSEUM, 1S93. 



The first to be described lies at Mayers Station , ou the stage road lead- 

 ing from Prescott to l*ii(enix, and some 28 miles southeast of the tirst- 

 iiamed town, which at time of writing, is the nearest accessible point 

 by rail. What stone has thus far been shipped is hauled by waoon to 

 Prescott, and by the Prescott and Arizona Central liailroad 70 miles 

 north to the Atlantic and Pacihc Railroad, which affords an outlet botii 

 east and west, as occasion demands. At time of writing there is how- 

 ever, in process of construction a new line connecting the Santa Fe 

 system on the north with the Southern Pacific, and which will pass 

 snffi(uently near the deposits to greatly diminish the hauling distance 

 as well as afford the benefit of competing freight rates furnished by the 

 two lines. The deposits occur on the western side of what for a con- 

 siderable portion of the year is a dry ravine, but which in the winter 

 and rainy season carries a variable and often turbulent body of water, 

 and rejoices in the name of Big Bug Creek. The country rock is highly 

 metamorphic schist standing nearly on edge with occassional dikes of 

 basic eruptives. The onyx proper occurs interbedded with a coarse 

 breccia formed ofschistose and dioritic fragments embedded in a sandy 

 and calcareous matrix, the entire formation occupying a low range of 

 hills, of which an area of 200 acres is estimated by the company to 

 comprise all the quarryable material. Standing at the stage station and 

 looking westward across the creek, one sees the low blufts of onyx where 

 the edges of the bed have been exposed in the work of exploitation. At 

 first glance the outlook is not inspiring. The rock weathers gray and 

 rusty brown, breaks down under the prolonged exposure to which it has 

 been subjected, and appears like anything but the beautiful stone it 

 really is. Closer inspection is, however, more assuring. At the shal- 

 low openings that had been made in the bluffs and on the top of the 

 hill, at the time of the- writer's visit (1891), the onyx occurred in 

 irregular somewhat concentric layers, (pi. 2), from the fraction of 

 an inch to 2 or more feet in thickness, and wliich are traversed par- 

 allel with the plane of deposition by wavy bands of color in all shades 

 of amber, white, ocher yellow, brown, dee}) ocherous red, and green 

 of a most beautiful emerald shade. The sound layers of stone are 

 separated from one another by porous cellular layers, so that slabs 

 of large size can be obtained only by cutting parallel with the banding; 

 /. e., with the plane of deposition. This in itself is no drawback, since 

 the colors blend much better and the general effect is vastly richer 

 than when cut across the grain. No two of the openings show mate- 

 rial of exactly the same nature as to color and markings, or as to 

 size and thickness of the blocks. In all, the stone lies in layers 

 readily separable from one another, and which, as a rule, thicken 

 and thiu out irregularly. The more highly colored varieties carry, 

 as shown by analysis, nearly 5 per cent, of carbonate of iron. Through 

 •the oxidizing effect of percolating solutions this carbonate has in 

 many instances been converted into a more or less hydrated oxide, 

 whereby the green is changed to red, brown, or amber-yellow colors in 



