Prof. Aasted on remarkable Mineral Veins. 553 



The main lode of the Cobre is cut off to the west by a cross-course, 

 after being heaved by several slides of small amount. The whole 

 workings on the principal vein are limited to a linear extension of 

 800 yards, and to a breadth of about 200 yards. 



The lode appears to have originally afforded superficially a great 

 breaudi of ferruginous earthy mineral (gossan) rich with black 

 oxide of copper, together with red oxide and carbonates, to a depth 

 of 16 fathoms ; beneath this, solid sulphurets occupied three courses 

 of ore, now being worked. The northernmost is of large size, 

 though variable, and underlies to the south ; the middle and the 

 southernmost courses are smaller, and nearly vertical ; all three 

 apparently approximate downwards. The " ground" is highly 

 mineralized both between the courses and outside the walls of the 

 two outer courses. The Cobre mine is open at present to the 160 

 fathom level below adit. 



Having thus described the position of the lode, the structure of 

 the "country," and the dimension and contents of the lode, the 

 author next noticed in detail the heaves and oross-courses, the 

 breadth of the " orey ground," and the wonderful timbering and 

 ^'dmirable working of the mines ; and after some remarks on the 

 •. ccurrence of mundic and gypsum, on the veinstone, the tempera- 

 ture, &c., he recapitulated as follows : — 



The western or productive part of the Cobre lode includes three 

 courses of ore, nearly parallel to each other in strike, but gradually 

 approaching downwards. Two of them are unusually large and 

 rich ; the middle one is the smallest. The northernmost (on the 

 foot-wall) is affected by small heaves, and all the *' orey ground " is 

 terminated by a cross-course to the west. 1'he intervals between 

 the three courses of ore are occupied by a conglomerate or breccia 

 of decomposing porphyry and greenstone, abounding with lime, and 

 passing into a compact whitish-green porphyry. Associated with 

 the courses of ore, the veinstone, and the " country," are large 

 quantities of iron-pyrites ; and at a certain considerable depth the 

 veinstone contains gypsum. Regarding the three courses of ore as 

 parts of one great lode, nearly 200 yards wide at its crop, the lode 

 may be said to dip moderately, and the orey portions are chiefly 

 near the hanging wall and the foot-wall, but also extend in bunches 

 and strings into the intervening veinstone and into the enclosing 

 rock, which is highly mineralized. The courses of ore are super- 

 ficially indicated by a distinct gossan of spongy quartz and iron- 

 oxide, with highly coloured clays, beneath which are oxides, carbo- 

 nates, and sulphurets of copper, succeeded by sulphurets of copper 

 and iron, the latter gradually preponderating downwards. The 

 " horses " or areas of unproductive ground within the lode and 

 between the courses of ore, consist chiefly of porphyry, like the 

 surrounding rock, and generally mineralized with iron and copper 

 pyrites. The metalliferous deposit, in accordance with the form of 

 the ground, terminates abrujjtly to the west, where the hill is pre- 

 cipitous, and dies away towards the east. Tlie heaves and cross- 

 courses do not carry ore. 



Phil. Mag. S. 4. No. 75. Suppl. Vol. 11. 2 



