Image provided by: University of Oregon Libraries; Eugene, OR
About The west shore. (Portland, Or.) 1875-1891 | View Entire Issue (Aug. 1, 1879)
238 THE WEST SHORE. August, 1879. MiNKitAi. ram. The imiv.Hni. f 1 correct theory concern ing mineral veins cannot he overestimated, uir ticularly on this coatt where prospecting for the precmus metals in so common. The alieenco nl proper b now 1I i" haa diaeppiinted tin- hocii of many, who, deceived liy small pocket limli or paiti.il strikes, waate their mean in the at tempt to dcvolop au illinium In the bop of. satisfying many inquiries concerning the appa rently controverted subject of mineral veins, wa llml in l.i- ("onto "I i - 1 , " publiilicd by I. Applelun k Co., V V., a clear illuitratinn of the ayaUitn : All rocks, hut eaiecially mrtamnrphic rocka in mountain regions, are seal I ami mmd in every direction, m if broken ami again mended, aa if wounded ami again healeil. All 1110)1 teams ami soars, nf whatever nature ami by whatever pi"- formed, are often called t. tin general name of ivim. It ii Uitter, liowevur, that ilikea anil M called granite vemi, nr all nates of fiaanrea filleil at the moment of forma tion hy igneoua injection, ahmilil Ih acparatcd f con the category of vaina. True veins, then, are at , uiiiiilaliiiiin, iiiii I y in liiaiinia, ol certain mineral mattera utually in a purer ami more arry form than they exist 111 the rocks. The accumulation haa 111 all caaea taken pUot ajattajti Thua limilnd, veina are of three kimla I 'm. nl arurr.a-ima, ivihj " ii'filtrnlinn ami great MM ma. Thaaa three, however, graduate into each other in auch wiaa that it la often ilif licnlt to determine Ui which we muat refer any jiariicuiar caae .oine writer make many oilier kimla In veina nf segregation the vein matter iloea not littler greatly (mm the inclosing rock. Such are the irregular linae nf granite in granite, the linaa ilitfenng (Mm the mcl.aing rook only in color or texture; alao irregular tenia nf frMapar in granite or m gneiaa. 1' inter the aaine heail belong alan the irregular streaks, clnuila ami Mb hea, an nnmmoii in mail. I,- In these caaea there aeema t lie no illalinct line nf ecparatum laatween the vein ami the inchaing rock -no iiatwW wnll to Ikr mm. The rvaa.ni ia, theae e in. are wit (orninl by the lilliug ol a prevmualy etMhag nature, hut by the segregation of certain matenaia, in certain iptita ami aloug certain line Irom the general maaa of the rock, either when the latter wa in plaatio condition from heal and water, or elae by nieaua of percolating water, tnmewhat aa rnaerWinaj of lime, clay, iron or and hint are i..r 1 in the strata. em ol laliltraUnii originate in tnctainnriihic Iwokt which have probably Iwu subject.,! t,, pnwertal honauutal preeaure. Ileaiduathe wide (Ids mi which auch rocka are thu thrown and t"e great liaaurea the produced, the etrata are often broken into mall pie. . a hy mean of the eqaeaaing aad craahing. The amall tiuurea thua pn-lu. . -d are often Haw by l.ihml mtnlmm (rata the walla, or elae hy alowly ier'uUting water holding m solution the mure aolulde matter contained in the rocka. The pr.. ,-a. ,. tiantlar to the tilling nl oaviUe left hv imbedded nrgautawa, and aull more u tb tilling i air bleb ta trap, and lav aa. and the formation of aflatea and oaraaltan nmygdulea In vein nf that kiad. theref.w, a Iteauttfal nMn atxjajajtj M often prodned by the auixwasire deu.au.iion ol diflei. nt ndoreal matenaia on the wall of the heeure. Veins nf thi kind alao, aiuce they are the tilling of a prriiouejy euetieg liaaure, Lav, I tt mm 1 waitta. The hlling consuls mt coav manly of stlioa nr id carUwate of lime. Kiaaure vein are lilumn of the itreat liaaurea induced hy movement of the earth crust iv ana taaa naeurca are tilled at the loaitwltoa by urneout injection they are called .fate, hut if aulwe.pi, 1, tit with mineral matter, hy a different proa-eat. Is tar di. iitaod hereafter, they an jtatnrr nw. Thaaa veina, tkmtfim. like dikea, outcrop over the mrfaco of the country often for many mile, 50 or more. Like dike alao they aie of leu many yard in wmtli, and eitend to unknown hut certainly very great depth. Like dike and liaaurea alao they occur in parallel iytem. The moat olivinim charoctoriticH of the vein of thia claaa arc their nj.c, their continuity for great diatancea and to grrnt depth, and their nccurrencc 111 parallel Hyatcm. Ah the vein in a tilling nf a pruvioualy exiatiug liaaure, thedis tim torn Iwtween the vein and the wall-rock is uaually ipiite marked. In many caaea, in fact, the vein tilling i HcparaUil from the wall-ruck hy a layer nf earthy nr clayey matter called a rliiijr, as if the Hide nf the ojk.ii fiBfuiro had 1, 1. ..in foul hy H-rcnl,iting water carrying clay, before the liaaure waa tilled with mineral matter. The OOQetunl nf liaaure vein are alaO no. 1. aeiiucnt movement reopened the flaaure to It b' b' and tore away thehorae . after whioV. .- - waa again tilled. Veins, of course, usually intersect the strata hut in some cases where strata-planet, or elae cleavage-planes, are highly inclined, the open, ing is between these planes, aud the veins are therefore, conformable with them. Some metals, particularly iron, occur prinei pally in great lieds, being accumulated by a process already described, Othera, especially lead, often accumulate in Hat cavities between the ttrata, especially of limestone. But mutt metals occur iu veina. All the kinds of vein mentioned above may contain metals, but the segregative veins are utually too irregular and uncertain, and the infiltrative veins too tmall, to lio profitable. True, profitable metalliferous veins are almost always great fissure veini. rw. t rf WI9. I no ' FW. Ii r in w I 1 it I 1 ir t lli I Wft I THKOKY OK MINKIiAl. VKINS, 1I.I.I STIIATKD tar more aned than th.nw ol other claaaea. Although more regular than other kindt, yet litaura vein are alao often ijuite irregular oinetiine branching, aometimr narrowing or (inching out in anme parU and wideniug in othera iKig. 1 1, aometiinee dividing and again coining together, and tbut incloaing a portion of the wall.rock (Kin. Ji. Such an incloaeil maat of country rw in the midst of a vein ia called a "aoraf. Many of theae irrtgularitioa are prohahly the reault of movemrnta after the nature waa formed, nr even alter it waa lillcd Ihua. if al.f.l (K,g, ) be , n o( irregular ein, then it It probable that ' e ,1 waa the original position of thu wall; Imt, be lore it waa tilled, it slipped up to iu preaeut uiaili,. Again, imxemenU may reoiien a fiaaure after it i tilll. In tuck caaea, if the adhr...,u of the lilliug to the wall i ttrong, lair Uuttt of the wall r;k are torn away: and if a "" I 1'1'ng take place, a "boree" u furme-L Thtu a a a aad b b h (Kig. '.'I represent the Hf original walU ol an irregular rain; but tub The contents of metalliforout veina are of two goueral kimla, via., iviVafa and ores. The principal vein-ituffa are iluartx, oarbonaU ol lime (calc apar), oarbonaU of baryta, carbonate of iron, sulphate of baryta (heavy tpar), and fluoride of calcium fluor-spar). By far the moat common of theae it quart, and out ia calc spar. OfU-u, however, the vein-stud it an aggregate f minerals forming a true rock. Nearly the whole of a vein oooaiata usual h of vein-stuff. The ore exists in comparatively amall quantities, sometime forming a central rib or sheet, aa ia deposited hut (Fig. 31; sometimes in irregular isolated maaaet oalhol bunches or ocketa, or in small strings, or graiaa. irregularly scattered through the vein-atuS and ei lending often a little way into the wall-rook. The chemical form in which metal occur art 'ery variout; aometimet they occur as par metal (u always in the oaf of gold and plat inum, and sometimes in the caae of silver and copper), but more commonly in the font of metallic .nlphidea, metallic otidr and metallic