OATHILL DISTRICT. 355 



ciation of tlie Oatliill mines. Hot sulphur springs issue from an opening 

 of the abandoned Valky mine at Lidell. The rock is highl}- metamorphic 

 and shows small quantities of cinnabar associated with black opal. The 

 ^Etna Company's deposits are in part in metamorphic rocks, showing at 

 present no evidence of volcanic action, unless the evolution of large quan- 

 tities of inflammable gas is to be regarded as due to causes coming under 

 this category. These metamorphic rocks, as well as the strata at Oathill, 

 are members of the Knoxville series. Two of the ore deposits are in part 

 impregnations and in part of the irregular, reticulated t3'pe. In two of the 

 mines of the ^Etna Company the deposits form veins or vein-like impreg- 

 nations at the contact between the basalt dikes and sandstone, the ore 

 occurring both in the decomposed basalt and- in the adjacent sedimentary 

 material. No hot water or gas now reaches these veins, though they must 

 be of very recent origin. There is no reason whatever to suppose that the 

 various deposits of this small district are due to essentially different causes, 

 and the common cause seems beyond question the action of thermal 

 springs. 



strata of Oathill. — Tlic deposits of Oatliill are inclosed in a gray, rather 

 friable sandstone, which is comparatively little altered or disturbed in the 

 neighborhood of the mines, but passes over into intensely metamorphosed 

 rocks in all directions. Veinlets of quartz, however, intersect the sandstone 

 in some places, indicating that the general metamorphism of the country 

 was feebly felt even here. The sandstones are not fossiliferous, though 

 Aucclla concentrica occurs at no great distance and evidently in the same 

 series of strata. A small amount of .shale accompanies the sandstone. The 

 area of unaltered rock is small, the ridge at the north end of the map (Plate 

 V) being highly silicified, while the southern border is in serpentine, which 

 forms a part of the belt of this rock, extending from the ^Etna mine north- 

 westerly to St. Helena Creek. 



Lavas. — Thc liill iu wliich the deposits occur is covered over with a thin 

 layer of basalt. This sheet is cracked up into large bowlders, many of them 

 weighing many tons each, and the underlying sandstone is expo.sed at a num- 

 ber of points. The basalt is for the most part gray and vesicular, but is found 

 in the more usual dai'k, compact form at a few points. At the northwest cor- 



