June 1, 1889.] 



KNOWTLEDGE ♦ 



163 



have, some considerable time after deposition, undergone 

 changes and, in many cases, have been subjected to great 

 heat, to violent upheavals, disruptions, and compressions, 

 with the result that they have become more or less crystal- 

 line, and frequently flaky or schistose in structure, and are 

 traversed by numerous cracks and fissures in which quartz 

 has accumulated, and, with it, gold in many instances. The 

 rocks in which these auriferous quartz veins are generally 

 found are those schists which are named from their pre- 

 dominating mineral chloritic, talcose, micaceous, or horn- 

 blendic ; it is found less commonly in diorite, in porphyry, 

 and sometimes in granite. These rocks often contain gold in 

 very minute proportions, which becomes sometimes more 

 prominent in the vicinity of a fissui-e or crack, but it is never 

 present in quantities which would permit of the idea being 

 entertained of its commercial extraction from this so-called 

 " country " rock ; in the intersecting quartz veins, however, 

 gold is frequently found in paying quantities, and such veins 

 constitute the "gold reefs " found in difterent paits of the 

 world. Gold is never found in these veins in continuous 

 bands, as is the case with other metalliferous deposits ; but it 

 occurs in patches and accumulations, here and there, in the 

 vein ; such patches are known as bunches, shoots, pipes, 

 chimneys, according to the length, breadth, size, and po.sition 

 of the accumulation. In some cases veins are filled with 

 pyrites instead of quartz, or sometimes, in fact very fre- 

 quently, both are present, and the pyrites is found to contain 

 gold ; it then appears not to be so bunchy aa when it exists 

 in the quartz veins. I have seen in Colorado thick bands 

 of auriferous pyrites, which, from their appearance in many 

 adjacent mines, may be presumed to be many hundred yards 

 in length, and apparently more or less continuous. Gold 

 tellurides are also found in veins in Transylvania, in Hun- 

 gary, and in Boulder County, Colorado. 



Gold, however, does not exclusively occur in reefs ; in 

 fact, the largest supplies have been obtained from "placers," 

 where it occurs in beds of sand or gravel, which have been, 

 or are even now, the beds of rivers. Other instances are 

 known where gold occurs in deposits consisting of fragments 

 of rock cemented together by silicious material, forming 

 what is known as breccias, or conglomerates, or pudding- 

 stone, or, in the Transvaal, as banket. 



Both the auriferous sand and the banket owe their origin 

 to the destruction— which is constantly going on now, and 

 has been going on ever since the rocks have existed — of the 

 auriferous rooks. The detritus, in the case of the sand, has 

 been carried down the rocky slopes by streams of water, 

 which have dissolved much of the rocky material, and 

 carried away light particles, wearing away larger ones, and 

 allowing the heavy gold and wear-resisting quartz to 

 deposit themselves. In course of time the former has 

 become concentrated in those parts of the river where the 

 current has been interrupted by bends, &c., for the simple 

 I'eason that the sand, being lighter, is to a large extent 

 washed away by eddies of water which would not be 

 sufficiently strong to move the heavier particles of the 

 precious metal (the .specific gravity of quartz is SCi, while 

 that of gold is about 19). Such .accumulations are called 

 " pockets." The " banket " deposits po.s.'-ibly originate in 

 much the same manner, only the conilitions being favour- 

 able, much of the detritus, which ha.s become pulverised, 

 and concentrated as regards gold, as in the case of the sand, 

 has subsequently acted as a cement to the larger fragments, 

 and so given rise to the present deposits. 



There is still another form of deposit in which gold is 

 found, and which is also derived from the destruction of 

 older rocks. In lliis case the amount of water has been 

 liaiited, and consequently the more refractory products of 

 decomposition, instead of washing away to form banket or 



sand, remain on the spot or near it ; moreover, they re- 

 main in great blocks permeated with vesicules and holes, 

 which represent the positions previously occupied by the 

 less refractory constituents, these having succumbed to the 

 action of the various constituents of the atmosphere ; that 

 is to .say, the moisture, the carbonic acid, and oxygen. The 

 minerals left behind are principally quartz, some iron oxide, 

 and gold, if present in the original rock ; some of the gold 

 will, however, dis.solve. These spongy-looking depo.sits of 

 ferruginous quartz are known as " gossan," and are generally 

 found whenever the out-crop or the upper part of the lode 

 is exposed to atmospheric action. If we take into considera- 

 tion the enormous number of years during which these 

 changes have been going on in nature, it is easy to realise 

 that very extensive deposits of this description may have 

 been brought into existence. They would, of course, be 

 more localised than the banket deposits, which in their turn 

 ought to be more localised than the alluvial or river 

 deposits. The famous Mount Morgan mine in Queensland, 

 Australia, is an instance of a deposit produced by atmospheric 

 influences. 



In alluvial deposits and in the various matrices the gold 

 appears in many states of aggregation, which have received 

 various names : — In nuggets, or pieces of irregular shape 

 and of moderate size, in gi-ains more or less crystalline, 

 down to powder which consists of individual particles 

 invisible to the naked eye ; or it occurs as thin sheet gold, 

 leaf gold, foliated gold, down to mere films of gold ; and 

 sometimes in long, thin aggregates of gold, such as that 

 known as wire-gold, of moderate thickness, down to mere 

 threads of gold. 



Gold is found in all parts of the world. In Europe it is 

 found in largest quantities in Transylvania, and in Hungary, 

 where mines were worked by the Romans. It is also found 

 in Spain, in North Italy on the northern slope of the 

 Alps, from Monte Eosa and Simplon to Aosta, in Sweden, 

 in Wales near Dolgelly, in Scotland near Leadhills, in 

 Ireland in county Wicklow ; whilst auriferous sands exist 

 in the following amongst other rivers : Rhine, Rhone, 

 Reuss, Aar, Danube, and many Cornish streams. 



In Asia gold is found in the Ural Mountains, where it 

 was probably mined by the Scythians ; also in Siberia and 

 in many other parts of Asia, notably India. 



In Africa it occurs on the west coast, near Ashantee, 

 known as the Gold Coast, and in the Transvaal, which 

 is now so famous; it has been said that Matabele 

 Land is one of the richest gold districts in the world. 

 On the coast of Mozambique there are gold mines 

 which are supposed to be the same which existed in 

 Solomon's time under the name of mines of Ophir, which 

 name has lately been applied to certain properties in that 

 district, recently put on the London market. Gold also 

 exists elsewhere in Africa. 



In America, North, South, and Central, gold is 

 very widely distributed. It is found in Mexico. In 

 the United States, the gold mines of North Carolina, 

 Virginia, Georgia, and South Carolina were once the 

 great source of gold, but the discovery of gold in 

 California in immense deposits soon eclipsed these and all 

 other known gold deposits in the world ; the subsequent 

 discoveries in Australia, however, equalled them. Other 

 States are gold pi'odncors — Colorado, Arizona, Idaho, I'tiih, 

 some of the Eastern States, the newly created States 

 Dakota and Montana, and the territories of Washington 

 and Oregon. British Columbia and Vancouver's Island 

 have gold — the former promises well for the future ; so has 

 Alaska; whilst gold is also found on the eastern side of 

 Canada and in Nova Scotia. In Central America gold occurs 

 in many places, including Honduras, Costa Ric:i, etc. 



