178 REPOET OF NATIONAL MUSEUM, 1899. 



In many places these porous tufas and breccias are richly charged with 

 sulphur, which fills all the interstices of the rock and sometimes lines 

 large cavities with layers of crystals 5 or 6 feet in thickness. In the 

 Rabbit-Hole District sulphur has been found in paying quantities for 

 a distance of several miles along the border of the desert, but the dis- 

 tribution is irregular and uncertain, and is always superficial, so far 

 as can be judged l)y the present openings. The sulphur has undoubt- 

 edly been derived from a deeply seated source, from which it has been 

 expelled ])y heat, and escaping upward along the lines of faulting has 

 been deposited in the cooler and higher rocks in which it is now found, 

 though whether the deposition took place by direct suljlimation or 

 through the decomposition of hydrogen disulphide can not now be told 

 with certainty. Judging from the siliceous material that cements the 

 tufas, it is evident that the porous rocks in which the sulphur is now 

 found were penetrated by heated waters bearing silica in solution pre- 

 vious to the deposition of the sulphur. The mines occur in a narrow 

 north-and-south belt along a line of ancient faulting which is one of 

 the great structural features of the region. The association of faults 

 with sulphur-bearing strata of tufa is here essentially the same as at 

 the Cove Creek Mines, yet to be noted. At the Rabbit- Hole Mines, 

 however, no very recent movement of the ancient fault could be deter- 

 mined. This absence of a recent fault-scarp, together with the fact 

 that the mines are now cold and do not give oft' exhalations of gas or 

 vapor, shows that the solfataric action at this locality has long been 

 extinct, though at the Cove Creek Mines, mentioned below, the depo- 

 sition is still in progress. 



According to A. F. Du Faur' this Cove Creek (Utah) deposit is in 

 Beaver County, near Millard County line. It was first discovered in 

 1869, but owing to lack of railroad communications remained undevel- 

 oped until 1883. The region is one of comparatively recent volcanic 

 activity. The sulphur occurs impregnating limestone and slate to such 

 a degree that very pure pieces as large as one foot in diameter are 

 obtainable. It also occurs impregnating a decomposed andesite (Speci- 

 men No. 14921, U.S.N.M.). The Cove Creek mines are situated about 

 2 miles southeast of Cove Creek fort and to the east of the Beaver road 

 in a small basin near the foot of the Sulphur Mountains, surrounded by 

 low hills, with a narrow ravine opening in the west-northwest direction 

 into the plain. The basin is about 6,000 feet above the level of the 

 sea, while the Sulphur Mountains to the east rise about 2,000 feet 

 higher. The hills surrounding the basin consist mainly of andesite, 

 partly also of a very light white trachyte. 



As far as explored, the sulphur bed extends at least 1,800 feet by 

 1,000 feet, and the quantity of sulphur containcHl therein was estimated 



1 Transactions of the American Institute of Mining Engineers, XVI, 1888, p. 33. 



