VEIN STKUCTtlKE OF VAUIOUS MINES. 415 



face this cap clumiber was connected with a system of tln-ee parallel fissures, 

 two of them carryiiii^' ore and being in fact well developed and lunnistak- 

 able chambered veins. Their contents varied in value from i)oiiit to [)oiut, 

 as tliat of all veins does, but they have yielded large quantities of ore. 

 The third fissure has been proved to exist, but at the one point where it 

 was intersected it carried only pyrite and no ore. In the main uiine at 

 New Almaden tliere exist two parallel fissures separated from each other 

 b}' but a short distance. Ore is deposited in and near them, so that they 

 are true chambered veins. From the lower levels they ascend on diffurent 

 courses and reach the surface at a considerable distance from each other. A 

 great wedge of country rock is included between them, and fissures attended 

 by ore penetrate this also, foruiing chambered branches of the main veln.s. 

 But perhaps the finest and most interesting examples of vein structure are 

 afforded by the grouji of mines near ^Etna hot springs, which issue from 

 one of them, while two others lie at the contact between basalt dikes and 

 the inclosing sedimentary rocks. As was noted above, there is no reason 

 to suppose that this group of adjoining deposits owes its origin to various 

 causes; indeed, the supposition that the}' did so would be nothing less than 

 extravagant. Here the bodies adjoining and in part penetrating the dikes 

 are un(piestionably chambered veins, but still more striking are those in 

 the main workings of the Napa Consolidated mine at Oathill, called the 

 Mercury vein and the Manzanita vein. These occupy nearly parallel fault 

 fissures in nearly horizontal unaltered sandstones. The faulting was accom- 

 panied by compressive stress, as is proved by the fiexure of the strata in 

 opposite directions near the fissures, and the two principal fissures were 

 doubtless produced at the same time. Parts of these veins are simple 

 fissures filled with vein matter, which does not extend beyond the walls, 

 but at a number of points impregnation of the adjacent sandstone has taken 

 place. As a whole, therefore, these deposits, too, are to be classed as cham- 

 bered veins. The upper portion of the Phoenix seems to have been a cap 

 chamber, and this is the character of most of the smaller deposits in the 

 State. The Great Eastern and the Great Western are both chambered 

 veins, and no better example of this form of deposit could be given than 

 die Elvan Streak of New Idria. 



