MINING LECTURE.

Te Aroha News, Volume III, Issue 131, 5 December 1885, Page 2

MINING LECTURE.

Mr Montgomery at Waiorongomai and Te Aroha. On Monday last Mr Montgomery (accompaniod by Mr McLynionfc), arrived at Waiorongomai and the sanid evening lrctureil to a large company of miners and local residents in the Public Hall, on the subject of Mineral Veins, Quartz Reefs, etc. Mr G. Wilson was called to the chair, and introduced the lecturer to his audi> enee. Mr Montgomery had a mrnner of Inrg** coloured diagrams suspended at the back of the stage to which he frequently referred to illustrate his subject as he proceeded. The lecturer was listened to With great attention. • , On Tuesday Mr Montgomery spoilt most of the d »y in visiting the urines at Waior.mgonni, b.ittery, etc.^ the s ev(»uing being devoted to imparting inatrnction in the use ol t,he blmv pipe, >vh.ch oocuy>Atioii proved so attractive that the

resumption of the4kx^Bttt&^t§bfd lecture was set asidlfi&wswJM£ . On^WeilnesilayM M^*^hWoinery ; /visited Hhe reefs i lftfflh i e^fvicjn i t jyof ■ the I'M Creek, hct eprfngs; fete., and in 'the, evening lectured tv thtrCfyirt HonseJ Ttf Arpha, (the Public Half l)eiug- engage.! .for a dan&e),t6 a, most aftfuiive oudi* ence, illustrating./his .übjecte^fetWaiorongomai by, aid of\hi«v dingram% the lecture was much appreciated. 1? Appended will be found A few note^Jn tje lectures referred to ;—; — ' **^ The mineral substances known to Hid miner are very varied, and found under a ! vauety of circumstances. Gold for in- ; stance occurred in river gravels, and in i rocks of varying: geological ages. Coal was not found in lodespbnfc was found in seams ,or , beds. Iron and copper ore wer« sometimes found in lodo9 and some times" "in seams or hirers. To distinguish the 1 modes in which different minerals were found was most important ;- A difficulty once occurred in Otago though lack of this knowledge, where a stratified deposit of copper pyrites was taken to be a lode, and tiie niners prospected for it in an altogether impossible locality, and a great deal of money was thus uselessly expended* The principal mineral deposits might be elassißed into tabular and alluvial deposits ; auriferous quartz reefs, being about the best representative of the lodes, and coal of seams. Lodes were formed through the ren ling of strata and the deposit of mineral matter within it, while seams were contemporaneous with the adjacent rocks. Contact lodes, of which the Gomstockj in America, was an example, occurred be* tween two different geological forma* tions. The mineral mai ter was not of tl c same character as the enclosing rock. Quartz reefs were composed of quartz, gold, silver, copper, antimony, galena, and other substauces j while the enclosing rocks, at the Thames, were of volcanic formation, ana elsewhere they consisted of schists and slates. Lenders, feeders, or droppers, were irregular biauclies running off from main reefs, and were otten met with, and were probably due to the shaking of the rucks when the fissures were first opened. In some districts sumll ivofs known as companion lodes were fonnd, parallel with main lodes, although quite independent of them. It wns not «asy to determine the length and depth of lodes. In Cornwall there were some which extended as far as 12 miles, while in America some were said to have been traced as far as 100 miles. In Transylvania, lodes no thicker than a sheet of paper, l>ut containing gold and tellurium, were worked profitably. The giea& Comstock lode in America was 500 or 600 feet wide at its outcrop, and the main lode *t ISilverton whs of immense size. Reefs from 20 to 100 feet in thickness weie not uncommon. The depths to which reefs descend is hot known, but in the deepest mhw in the world' in Bohemia, where operations are carried on at a depth of 3600 feet they are quite as strong as was the case nearer the surf -ice. Nearly all useful minerals were foun- in lodes, the exceptions being rock salt and coal. Platinum, and the allied metals, osmium and iridinm were not often found in reefs. Iron occurred in both lodes and layers, in the former case in the shape of pyrites. The metals commonly fonud in reefs were gold, 'silver, antimony, copper, arseftin, lead, mercury, manganese, and bismuth. With the exception of gold, and to a certain extent ailver, they We c raiely \n metallic form,; but were 'generally I'oinbin* I with flnn- metallic <*nb* stance?, nms Im-mim; ores The m>st fn'queiil couibiuutio is of metals neve witli sulphur, as sulphides c»f tea'd (also known as galena) - f erF :rttin.ony, of mercury _ riorminir cinnabar), and! of zinc (in tin' (Wf'n of Mend or black j.mk) f with <rxyk«'ii, a.s ii&idf* <»f in>u (or hematite), of c >pper, antimony^ or tin ; wit i earUmio acid, .i» c irbonates, an I also in the form of silicates, etc. Lodes were chiefly composed of qnurtss, carbonate of lime, brown spar, heavy spar, sulphate of limp, taFc, and Tarious clayey matters. The frequent occurrence of " sheken-sides,'* or polisiitd siricted surfaces caused by the motion of oner part of the rock vipou another, in deposits, pointed *o inovtMitents «>f the country rocks on the fissure during the formation of * lode. Surface workings were frequently more valuable than those at greater depths. Cianges in strike and dip ofteii have an appreciative eff«ct upon the richness of a mineral vein, but the variations are so it regular that no rule can be formnlated. Mr Montgomery refefrred to Ihe method of calculating the extent of " down throws"- by observing the segue cc of the strata. The amoflnt of heave was determined according to the extent of down-threw, and if either were ascertained, the other could easily be fotrnd out., the downthrow being equivalent to the vertical distance between the disconnected portions of the roef. The direction of the striae or scoring on the " si U ken- sides" found in some slides, were evidence of the direction of the thtovr. The fa iil ter might, either be a clay lode or an ore lode. Deviations » which were of radically different origin, wore sometim a mistaken for faults, for a deviated' 'lode tmist generally be of more recent formation than the body which deviated it. Fat Its were of regular dip at different levels, but deviations -were sometimes quite irregular as to inclination. Faults were of different lengths, and, like lodes, frequently wedged out, or divided^'into' different portions He said the"'conclflsions he had coma to were that reefs were originally fissures , caujse.l by the contraction of the earth's 'iriut, by earth- , {uii«es«, or by >oic:»nic eruptions; and that they were filled with mineral matter