SHALES FEOM HOIf-PEH, CHINA. 495 



well-preserved fossils, amongst which are gigantic specimens of 

 Orihoceras. 



At a distance of about 50 miles west of I-Chang, the Great-Lime- 

 stone series begins to be overlain by shales and arenaceous beds 

 interstratified with thinner limestones, the latter at first predomi- 

 nating, with a general strike N.W. and S.E., dipping S. and S.W. 

 at high angles and sometimes folding over in anticlinals. These 

 rocks are more disturbed than the thick limestones, but not faulted 

 or showing any intrusions of igneous rocks. Further west the 

 series increases in thickness, and shales predominate, having a uni- 

 form characteristic red-brown colour with occasional greenish-grey 

 patches. Some of these shales are slightly micaceous, others contain 

 small cavities filled with crystallized calcite. 



In the valley of Lukaho patches are found in which the shales 

 are impregnated more or less with minerals of copper, the beds con- 

 taining this metal being of the grey colour above noticed, regularly 

 intercalated with the red series and otherwise undistinguished from 

 these. The commonest form of occurrence is that of light green 

 films and specks of malachite or chrysocoUa in the cracks of cleavage 

 and stratification of the soft argillaceous rock, which is very friable 

 on weathered surfaces. Another form is a siliceous band, containing 

 specks of cuprite with the green oxydized minerals, also conformable 

 with the shales, but of irregular extension and more contiguous 

 to the calcareous and sandy beds. Accompanying both these, 

 occasional lumps of comparatively pure copper-ore are found enclosed 

 in the soft strata as in actual clay-seams, and it is this latter form 

 of occurrence which must be the origin of the peculiar wood-shaped 

 specimens examined at Shanghai and mentioned above. The extent 

 and value of these cupriferous patches, hardly to be called metal- 

 liferous deposits, could only be roughly estimated from the appear- 

 ance of numerous indications on the outcrops, none of which had been 

 opened up. In one case only was there evidence of continuity along 

 the strike of the strata up a hillside for a distance of some 200 yards, 

 and from this the richest specimens were obtained ; but the bed-rock 

 covered with detritus was not exposed sufficiently to give the size 

 of the impregnation in section. In other places the shales showed 

 copper coloration for a thickness of from 1 to 3 or 4 feet, the per- 

 centage of the metal appearing to the eye (unchecked as yet by any 

 assays) from a fraction of one to five per cent. The siliceous material 

 showed the nearest approach to anything like vein-stuff", the actual 

 richness of which (though certainly not high) could only be ascer- 

 tained by chemical test. 



The origin of these cupriferous patches, although not to be defi- 

 nitely traced by so cursory an inspection, must be ascribed to the 

 redeposition of the metal by infiltration of solutions derived from 

 other sources of unoxidizcd minerals in the adjacent rocks ; and as 

 the district seems to be devoid of any mineral veins, or even of 

 "pockets" of the ordinary metallic sulphides in the limestones, it 

 seems probable that the primary sources of the metal must have 

 been of sedimentary origin. 



