Bisbee daily review., 1909-05-26
MINING EXPERT TELLS IF ROCK
 HAVING VALUE

Extracts from an article by Cor don Surr, Mining Engineer. in the Mining world)
 Copper.-Copper occurs in various rocks. as the following examples will show: In the Lake Superior region giomeratc. amygdaloids and sand. stones; at Butte. the ores are in gran ite; in the Clifton district, in lime stone. and at its contact with DOT phyry, also in the latter rock; at Bis bee. in limestone: at Bingham, III porphyry, and, to some extent, in ed rhyolites: at Ducktown. in mica schist, in which occasional bands of gneiss occur: al Rio Tinto. between porphyry and schist: at Cerro de Pas co in adesite; in the Cobar district. New South Wales. in slates: in the Kantanfa region. Congo Free State. in sandstone; and in Cornwall, in clayslate and granite. It is worthy of note that where copper deposits are associated with limestone, and other rocks. either iGneous or sedi- mentary. the ore bodies are apt to be much larger and richer in the lime stone: this being also often the case with ores Of other metals.
 Lead.-Lead is usually associated with limestone. Among exceptions may be noted the great lead-silver de posits of the Occur d'Alene district, which occur mostly in quartzites. the metals being thought to have been deposited from ascending solutions derived from an underlying mass Of
 mopzonite The ores of the famous BrolSne Hill mine. Australia. which contain lead, zinc and silver sui' phides. are in crystalline schists.
 Silver-Silver ores are met with in various formations. limestone be ing a common country rock, frequent ly, however. associated with igueous
 rocks Many deposits os both silver
 and gold in the lands and islands bordering the Pacific ocean occur in or in connection with, andesites and allied rocks. and among examples
 may be cited the Comstcok lode. and the ores of Tonopah. numerous silver veins in Mexico and Peru, and va rious gold and silver occurrences in
 Japan. the Dutch East Indies. and 1 New Zealand. The veins Of Cobalt
 which carry native silver. cobalt and
 nickel are fin diabase and gabbro.
 Goid.-The sentence, Gold is
 where you find it. is often quoted but necessarily anything else must ! likewise be where it is found: gold
 however. Is very widely distributed
 in small quantities, and it occurs in rocks of all kinds. although in most cases the vein matter Is quartz. ol
 largely silicious. and pyrite is also a
 common associate. The amount oi gold required to make an ore is but
 trace compared to the more abund ant metals. which may partly account
 for the existence of gold deposits Tn
 many formations Ore. for example assaying s10 per ton contains little more than one six-hundredth part ol 1 per cent of gold. which quantity say. of copper ore lead, would alto
 gether escape detection in ordinary assays for the latter metals. In com mon with most mineral veins. gold
 bearing lodes generally occur in re gions which have been subjected to movements. accompanied as they ire quently are. by intrusions of igneous rocks. and those who lay great stress upon what they are pleased to term true" Assure veins. should bear in
 mind that on the Rand the gold is found in quartz conglomerate beds.