LODE. 



fcribcd, tut mud be fecn and Riidied to be underftood, and 

 vith which (kilful miners are converfant ; but the mofl ex- 

 perienced is liable to hive his prediiftions falfified by the 

 fluctuating nature of thefe hidden receptacles of various 

 matter. 



The indications mol depended on, in formina^ a iudg- 

 ment of the value of a lode, are derived from conlidcring the 

 fullottiusr circuniilances : 



1. The nature of the fubftances contained in the vein. 



2. The kind of rock in which it is found. 



3. The width zrA regularity of the vein, confidering, at 

 _lhe fame time, its direftion and dip. 



4. The ftruclure of the vein, fuch as the being open and 

 pervious to water, or, on the contrary, hard a:id dole. 



Thefe fymptoms may be, on the whole, confidered as per- 

 taining to veins containing all kinds of metals, though vary- 

 ing in fome in a certain degree : thus a hard ctofe lode may 

 be favourable for tin, though not fo for copper or lead. 



When a vein is found exhibiting all or moll of the ap- 

 pearances which experience has determined to belong to 

 thofe which are productive, it is called a iiniilj lode, and is 

 generally purfued with vigour, and at an expence propor- 

 tioned to the prevalence and continuance of the favourable 

 fymptoms. 



We (hall endeavour to confider the principal indications, 

 according to the order above ilated, and point out the lead- 

 ing facts to be obferved in this important branch of a miner's 

 bufinefs. 



I. Of the nature of the fuhjlances nmained in the vein. 



Thefe fubftances vary according to the depth to which 

 the lode is opened ; thofe near the furface being generally 

 different from the contents of the vein deeper under 

 ground. 



The iirft thing for which a miner looks k what in Cornwall 

 is called goffan. This iubllaiice does not appear to have been 

 very accurately defcribed, but is apparently a decompofed 

 mineral of an iron-ochre colour, varying from yellow to 

 brown-red and chocolate-brown. It is of a fpongy, cel- 

 lular texture, of little fpecilic gravity, and is generally foft 

 and friable.^ It is probably the refult of the decompofition 

 of pyrites or mundic, together with quartz, and contains a 

 cxmCderable portion of iron, and not unfrequently a mi.^ture 

 of tin and copper ores. When thefe latter are prefent in 

 the combination, it is a mod favourable fymptom ; but even 

 without them, goflan on the back of a lode warrants a trial 

 to a certain extent- It can by no means be aflertcd, that 

 the moll proinifing goflans have always been- followed by 

 ore, on a further purfuit ; but perhaps tliere is hardly an 

 inftance of a lode rich in ore, which has not a bunch of 

 kindly gojjlm iomewhere on the back. 



The next tubitance, proceeding in depth, upon which re- 

 lianos may be placed, is muiulic, including in this name 

 pyrites of all kinds, whether arfenical or fulphuretted, con- 

 taining iron or copper. Mundic is found at all depths and 

 in all lituations in veins: it frequently furrounds bunches of 

 copper ore, and is therefore a favourable fymptom, as they 

 are approached ;, and indicates their decline, when palled 

 through on the otlier fide. It fhould,. however, be recol- 

 ledled,, that mundic isvery generally found, and thcrcloie it 

 muft not be depended on by itfelf. 



The earthy Jubilances, which are efteemed favourable to 

 the exillence of valuable metallic ores, are principally quartz, 

 going under the general name of fpar ; a kind of clay called 

 floohan ; and, what is not very abundant, Jiuor, diitinguillied 

 by the appellation of candied fpar. 



The (iril and the chief ingredient in vems, quartz, is 

 kindly,, when it is ia a loofe friable form, often cryftallized. 



and cementing detached fragnients of- killas atfd the other 

 fubftances before eniim.erated. It is unpromifing when io 

 a clofe amorphous form, and is then termed a Jbarp hungry 

 fpar.^ 



The J!ooian, or clay, generally forms a brar.ch or vein on 

 one of the walls of the lode, and feems to be the divifion 

 between that and the rock containing: it. 



The decompofition of the adjoining ftrafa fjems to have 

 been the orig;n of this f ibftance, which is called by fome 

 foreign writers \\\e faalhande. 



Belides fluor, on which miners are not well agreed as to 

 Its promifing afpeiil, and which is not often found in quan- 

 tity, are fome other minerals, hkewife of not very frequent 

 occurrence, but elleemed favourable ; fuch z& prion, a kind 

 of decompofed quartz, and peach or chlorite. 



Hitherto we have faid nothing of the judgment formed 

 by ores found in a lode ; it depends upon the following cir- 

 cumftances : 



1. The fituation, whether fiiallow or deep. 



2. The mode of depofit, whether ilightly fprinkled 

 through the lode, or forming (hoots or bunches of large or 

 fmall extent. 



3. The quality of the ore. 



Under the firlt head, moft miners agree that, as to cop- 

 per lodes, rich bunches of ore found near the furface are not 

 to be depended on as (liewing that a mine will be very pro- 

 ductive ; it having often been found that fuch depofits have 

 been followed by poverty at a greater depth. Tin and lead 

 are found nearer the furface than copper. When a lode is 

 fpotted with fmall quantities of ore, and the other fubilances- 

 are kindly, fuch as the goflan and fpar, the appearance is 

 promifing ; but when the lode is hard, and in other refpeftj- 

 unkindly, then fmall things of ore are not to be reckoned on 

 as particularly favourable. After a certain depth, a regular 

 branch, or, as it is called, a leader of ore of any width, oc- 

 cupying part of a good-fized vein, and increaiing or even 

 ftuctuating in fize as it is purfued, is on jhe whole the belt' 

 fymptom, particularly if connected with favourable accom- 

 panying fubftances. 



Under the head of quality of the ore as an indication of 

 future profpenty to a mine, it mull be remarked that no- 

 thing requires to be received with greater caution than pro-- 

 raifes of fuccefs fuppofed to be derived from the richnefs of 

 individual fpecimens. We are fpeaking now more parti- 

 cularly of copper lodes. Few, we believe^ of the moll 

 profitable mines produce much ore of the richer varieties,- 

 which indeed is feldom found to occupy veins of conllder- 

 ab!e width ; on the contrary, moil of the beft mines are 

 thofe which yield ore in large quantities, but poorer in me- 

 tallic content. This obfervation has been likewife made on-- 

 the filver mines of South America, according to the account 

 of Humboldt. Copper ores are found in a greater variety 

 of fpecies near the furface than they are in deptli ; and 

 therefore tl\e miner's experience only will ferve to difcri-- 

 niinate perfcftly on this point : but we wilh to put all who 

 arc concerned in mining on their guard againll a fallacious- 

 hope, too frequently excited by the alTay of a Hone of ore, 

 which in reality often predicts the very reverfe of what it ji; 

 Ilated to do by the artful or ignorant. 



II. The iecond indication to be attended to, in eflimating- 

 tlie profpecl of fuccefs on a particular vein, has been Ilated 

 to be The kind of rot i in •which it ist found. 



It IS unneceflary here to go into a voluminous account of 

 rocks, becaufe the great mines of England, as well as of 

 the worid, being found in fuch mountains as are conjeftured- 

 to be of very early formation, do not admit the varieties iii. 

 tliis relpeifl, which fome, who are asquainted onlv with 

 J other 



