1858.] VIVIAN NATIVE COPPER. 109 



appear, only near the surface, have been changed into haematite, the 

 same original structure being preserved ; and it is a question whether 

 such portions have not passed through the intermediate conditions of 

 brown peroxide. 



4thly. The occurrence of rounded pebbles of hsematite in the 

 lower beds of the New Eed Sandstone which skirts the north- 

 eastern side of these hills, indicates the probabihty of such rounded 

 stones being derived from the wearing-down of the lodes above de- 

 scribed, and would, in that case, point to a date for their having 

 been filled with ore at a period anterior to the great spread of oxides 

 of iron which appears to have taken place in south-western England 

 soon after the deposition of the coal-measures. 



Of these points, the change of sparry iron-ore to the hydrous per- 

 oxide is one of very common occurrence, and is especially notable in 

 Styria, Carinthia, Siegen, and those other countries where similar 

 ores have been followed to a considerable depth from the surface. 



The further change to the red peroxide shows itself less frequently 

 with satisfactory distinctness ; but at Somorostro, near Bilbao, and 

 in several of the lodes of the Siegen district, most interesting ex- 

 amples may be obtained, in which the rhombohedrons, originally 

 characteristic of the carbonate, now consist of hsematite. 



Dr. Livingstone brought with him from central Africa stones of 

 iron- ore, picked up on the surface, which presented exactly the same 

 series of changes. Some of these African pseudomorphous iron- 

 ores were from the gneiss west of Loangua River ; others from the 

 Zambese, west of Tete. 



The grand scale upon which this pseudomorphous action has pro- 

 ceeded is a reason for inviting attention to new instances, which 

 may aid us to explain the formation of iron- ores in their natural 

 repositories, — a subject still far from clear, notwithstandirig the in- 

 genious papers of Haidinger and Yolger. 



4. On Ajrboeescent Native Copper in the Llandudno Mine, near 

 Great Ormshead, North Wales. By Captain William Vivian, 

 of the Llandudno Mine. (Communicated by John Taylor, Esq., 

 F.G.S.) 



[Abridged.] 



It is well known that copper, like some other native metals, some- 

 times crystallizes in filiform and arborescent shapes; but in these 

 forms they are mostly diffiised through masses of mineral gangue, or 

 spread out upon the matrix, apparently unable to bear their own 

 weight. The symmetrical forms, however, to which we now refer 

 are seen by a microscope to stand up like a crystalline grove of 

 trunks and branches. 



The entire group is composed of separate crystals, strung out in 

 axial lines; the crystals under high magnifying powers show the 

 flat wedge-like octahedron ; but there is no uniformity ; each crystal, 



