GOLDMINING IN NEW ZEALAND.—No. 7.

Daily Southern Cross, Volume XXVI, Issue 3857, 1 January 1870, Page 7

GOLDMINING IN NEW ZEALAND.— No. 7.

(BY OUR SPECIAL COMMISSroiTEB.) We remarked in a former letter that the general strike of the reefs in New Zealand -W&s about north-east, and that a line drawn in a north-east direction through the Middle and North Islands would intersecl all the gold-bearing districts from Otago to the Coromandel Peninsula. Along this line quartz reefs have at intervals been discovered, and lodes have been worked for the past three or four years in Otago, most of which have nearly a north-east bearing ; but all, so far as my knowledge extends, are in the north-east quadrant. On the Thames goldfields the same course is observable in the principal lodes ; any variation usually approaches the north. Ihere is in some localities a local cross system, composed prineipallv of very small veins ; but I have never observed a prominent lode>ith an east and west bearing, or ia the south-east quadrant. u In the. taountain range which, extends from Cape Colville northward a large main reef, cropping at intervals, has been traced for about 55 miles. The bearing of this reef approaches more nearly to a meridional course than any of the other principal lodes. This north and south reef has been found at Matamata about 15 feet thick, and from here it has been found at intervals nearly all the way to McLeod's Claim at Coromandel, and also back{ofMania,Whangapoua,MercuryBay, and Tiroa, where the reef stands 200 feet vertical height, being composed of .crystalline quartz. At Tiroa the range and its characteristic breaks, but forms again at the back or lauranga opposite Ohinemuri on the East Coast, where alluvial gold is said to .have been discovered. The widest known portion of this reef is at Wakaroa, where it closely approaches to 300 feet in thick ness, and as far as the lode has been traced it forms the axis of the Coromandel peninsula, for a distance as before stated of 55 miles. Now whether this reef will continue and in a southerly direction beyond Tauranga, I am not prepared to declare, but 1 judging from my previous knowledge of reef systems in other goldbearing countries, and the researches from time to time made iu the country south of Ohinemuri by those who have prospected that region, I should expect (o find it continuous, and hence I designate it the mother reef. In California there is one main reeF, which traverses the country for a distance of over sixty miles on a north-west and south-east line. It has several companion lodes running chiefly parallel with it, but sometimes a few points off on either side These companion veins, although separated by a considerable distance at the surface, not unfrequently run in to ioin it at lower levels ; others, so far as proved, are separate and distinct lodes. All Cahformans, and all writers on the mining interests of that country, unite in recosmiBing and calling this prominent mam lode the mother reef. Th« great Mexican silver-bearing reef, winch has yielded its mibiona to the commerce of the world, extends for hundreds of miles occasionally cropping out boldly and again dipping on its course far below the surface. It is the mother reef of the country through which it runs. As far as the one main or mother reef of the Coromandel peninsula has been traced I can observe but a slight difference in its position and torm from those of California and Mexico. The only difference probably la that the companion veins will be found running into the mother reef at low angles, and not following a parallel course. In view of the undeveloped state of the ground at present, I am not prepared to speak confidently on this point, but from the appearance of McLeod's reef, and one or two others, I am inclined to think thai on one &ide of the reef at least the companion veins ioin the main Jode as above described. On the other band it might be inferred, from the old ,ro7kin fi8 on ihe ffupanea, that paral lol reefs do exist, but even these are verr little proved, Victorian quartz minors, especially those from the neighbourhood of Ballarat or the dunes, have much to learn with regard to the reef system of the Thames district, and are apt, before they become thoroughly acquainted with the field, to form a wrong hypothesis. In these portions of Victoria the reef system comprises parallel lodes extending for miles across the country in a direction nearly meridionally. In the Ballarat district the direction of the reeis range 'at from due north to 12 N.&., and they invariably follow the course ot the ranges ; and so accurate are they in their direction that they have been traced for miles by the simple aid of the compaBS. "With the exception of a slate formation which occurs at intervals round the coast line, the whole of the Coromandel peninsutais of volcanic origin, but, although found at different places, Tapu is the locality where the slate rocks p^rtouinrd. Ihe remaining portion of the I field is trachytic tufa exhibiting great variety of mineral properties and colours. Standing on the summit of the Kuranui hill, it is interesting to mark the varied tints ot the rooks Iving at the different shafts and tunnels along the Moanataiari, where avery t shade of green, blue, red, and brown is observable. Aparfc from being interesting, the study of these aeological changes would largely aid the prospector when searchintr for quartz reels, and many miners, of Thames experience, already entertain theories which largely assist in their mining operations. The main range is broken bv trans* verse ridges, and is traversed by" quartz veins and dykes of igneous origin, which latter have influenced these lodes in a peculiar manner. These dykes, like the veins themselves, do not always protrude through the surface : very many of the shallow workings have passed over them without any further change being observed than a few rounded boulders embedded in the tufa. Deeper works in the same locality having proved the existence of dykes beneath them, the same may be remarked of the quartz reefs, many of which do not exist on the surface, and drives to a considerable depth have crossed these caps, the miners having failed to observe any indications of a mineral lode. On many parts of the field, where dykes have been discovered, quartz reefs are found to flank them on either side. To illus« trate this I may instance Sweeney's Claim, where a drive passed through one reef, penetrated the diorite, and crossed it at right angles, and at a distance of 70ffc. broke through ifc, striking another reef on the other side of ifc. On the eas of the Moanataiari Creek, in the neighbourhood of the Dauntless, the Union, Dublin, Norwegian, and Sussex claims, a strongs - diorite dyke exists, running in a direction . about west and east, and having quartz reefs and veins ranning through it, , some of which are highly auriferous.. In other instances the diorite will be accompanied by onejingle reef ; and in certain localities they 'exist , - eatirely. independent of any reef'systetn whatever. Hence ifc is impossible t6 form »ay certain theory vriph regard to the

connection between the igneous dykes and quartz reefs. In many cases en this field drives are being pushed through the dyke formation with the expectation of striking reefs flanking them on the other side ; but, from the varied and peculiar forms that the reefs take in connection with the dykes, I must, from my experience announce it as my opinion that no certain theory can be established. The topographical formation of the country appears to have originated from the same volcanic agency which formed the dykes and rtefs. These dykes vaw in different localities, inere being s» marked distinction between those of the Tararu, the Upper Karaka, and those in the neighbourhood of the Moanataiari. The dykes partake of the peculiarities of the reefs in regard to the underlie, which is in some places S.E., and others to tha JN . W., and instances occur where no distinct uuderlie can be observed.