J. LeConte—Mineral Vein Formation. 425 
water still issuing from a narrow crevice in the middle, some 
is conspicuous and in some cases the filling of fissures by suc- 
Cessive deposits has given rise to a vertica 9. 
banded structure like that found in veins. 
Fig. 2 is an ideal section of such a vein of >i 
the natural size. This structure, however, =| 
3 as == 
previous observers. The deposits in many places are stained 
and clouded with metals, especially iron oxide and cinnabar. 
Wherever the issuance of the hot water is still going on slowly 
the silica is found in a gelatinous condition. Other observers 
have found in small quantities many other metallic sulphides, 
and even free gold is said to have been found in these sul- 
phides. Here then undoubtedly mineral veins are now forming _ 
under our eyes, but their metallic contents are in very small 
Kage aig 
ms to issue lower down to th I g 
found active vents and even feeble geyser eruptions which are 
said to have been more violent at one time than now. 
It will be seen then that there are indeed here fissures filled 
and now filling with quartz veinstone of ribboned structure 
and containing metallic sulphides, yet these are not fissures and 
‘iis: 
