GOLD 687 



Gold Silver 



Welsh gold: 



Welsh Gold-mining Co. . . . 76-40 2270 



Scotch gold: 



Sutherland 79'22 20*78 



WaulockHead 86'60 12-39 



Calif omian gold: 



Mariposa 81 '00 1870 



Russian gold: 



Boruschkoi 83'85 16-15 



Australian gold: 



South Australia .... 8778 6-07 



African gold: 



Ashantee 90'055 9-940 



Gold occurs in threads of various sizes, twisted and interlaced into a chain of 

 minute octahedral crystals ; as also in spangled or rounded grains, which, when of a 

 certain magnitude, are called pepitas. The small grains are not fragments broken 

 from a greater mass ; but they show by their flattened ovoid shape, and their rounded 

 outline, that this is their original state. Humboldt states that the largest pepita 

 known was one found in Peru weighing about 12 kilogrammes (26lbs.avoird.) ; but 

 masses have been quoted in the province of Quito which weighed nearly four times 

 as much. Some of the * nuggets ' from Australia have greatly exceeded this. The 

 specific gravity of native gold varies from 13-3 to 177. 



The mineral formations in which this metal occurs are the crystalline primitive 

 rocks, the compact transition rocks, the trachytic and trap rocks, and alluvial grounds. 

 Sir Koderick Murchison says, in a chapter On the Original Formation of Gold, in 

 his 'Siluria': 



' We may first proceed to consider the nature and limits of the rich gold-bearing 

 rocks, and then offer proofs that the chief auriferous wealth, as derived from them, 

 occurs in superficial detritus. Appealing to the structure of the different mountains, 

 which at former periods have afforded, or still afford, any notable amount of gold, we 

 find in all a general agreement. Whether, referring to past history, -we cast our eyes 

 to the countries watered by the sources of the Golden Tagus, to the Phrygia and 

 Thrace of the Greeks and Romans, to the Bohemia of the Middle Ages, to tracts in 

 Britain which were worked in old times, and are now either abandoned, or very 

 slightly productive, or to those chains in America and Australia, which, previously 

 unsearched, have in our times proved so rich, we invariably find the same constants 

 in nature. In all these lands, gold has been imparted abundantly to the ancient rocks 

 only, whose order and succession we have traced, or their associated eruptive rocks. 

 Sometimes, however, it is also shown to be diffused through the body of such rocks, 

 whether of igneous or of aqueous origin. The stratified rocks of the highest antiquity, 

 such as the oldest gneiss and quartz rocks (like those, for example, of Scandinavia 

 and the Northern Highlands of Scotland), have very seldom borne gold ; but the 

 sedimentary accumulations which followed, or the Silurian, Devonian, and Carbon- 

 iferous (particularly the first of these three) have been the deposits which, in the 

 tracts where they have .undergone a metamorphosis or change of structure by the 

 influence of igneous agency, or other causes, have been the chief sources whence gold 

 has been derived.' 



Gold is usually either disseminated through the rocks, often in extreme minuteness, 

 or spread out in thin plates or grains on their surface, or, lastly, implanted in their 

 cavities, under the shape of filaments or aborescent crystallisation. The minerals 

 composing gold-bearing veins are either quartz, calcspar, or sulphate of baryta. The 

 ores that accompany the gold in these veins are chiefly iron pyrites, copper pyrites, 

 galena, blende, and mispickel (arsenical pyrites). 



In the ores called auriferous pyrites, this metal occurs generally in an invisible 

 form ; but though invisible in the fresh pyrites, the gold becomes visible by its de- 

 composition ; as the hydrated oxide of iron allows the native gold particles to shine 

 forth on their reddish-brown ground, even when the precious metal may constitute 

 only the five-millionth part of its weight, as at the Rammelsberg in the Hartz. In that 

 state it has been extracted with profit ; most frequently by amalgamation with mer- 

 cury, proving that the gold was in the native state, and not in that of a sulphuret. 

 The iron pyrites of Wicklow and of some of our English mines, contain gold. After 

 the sulphur of the ore has been separated in the process of manufacturing sulphuric 

 acid, the residuary mass, called sulphur-cake,' is roasted with common salt. This is 

 thrown into hot water, the copper which is present is dissolved as chloride of copper. 

 The silver present has been converted by the roasting process into a chloride ; this is 



