Chrome Mining at Gundagai

8 June 1895 Australian Town and Country Journal

Mr. Geological Surveyor Carne's Report.

We have received from the Department Of Mines Mr. Carne's, F.G.S. (geological suveyor) report of the chrome deposits ir, the Coolac, Gundagai, and Tumut districts: which we have abridged as follows:

In the Guudagai-Tumut district, chromite has now been found at intervals in the Serpentine country, for a distance of about twenty-four miles southerly from the first deposit opened near Coolac.

The most southern operations being within eight miles of Tumut. Permits to mine extend to even a greater distance.

The most recently discovered deposits towards Tumut, such as the Emu, Mount Miller, Keefe's, and M'Inerny's do not at present afford indications of being equal in extent to the deposits nearer the Murrumbidgee River and Coolac, such as the kangaroo, Carroll and Gillespie's, Quilter's, and Vulcan Mines; but as little more than preliminary prospecting has yet been begun, more extended work may belie surface features.

About 1200 tons of chromite has been raised from the Vulcan Mine, chiefly by means of an open cut of a most dangerous character, which is now being filled in, preparatory to the adoption of a safer and more systematic method of extraction.

From the appearance of the remaining portions of the ore bodies, I am of opinion that my previous estimate of ore available in the then known bunches, viz., 2250 tons, will not be exceeded, though it is quite possible that prospecting may discover other deposits in the vicinity.

Between the Vulcan and Quilter's Mount Helena Mine, a distance of about five miles, several bunches have been discovered, but chiefly of minimum grade at surface. No ore has yet been extracted from them.

Of the six deposits of chromite on Mr. John Quilter's property at Mount Lightning, described in my first report, three have since .been opened, and 1100 tons of ore dispatched.

Both these deposits when first presented were very small surface outcrops from under the soil, and loose slipped rocks, which had not been removed, hence an attempt to give a roughly approximate estimate of quantity, based upon measurements of only partly exposed outcrops, has proved altogether futile.

I am informed by Mr. Quilter that four consignments aggregating 804 tons, yielded from 49.8 to 56.5 per cent, of sesquioxide of chromium.

On the south side of Mount Lightning, close to the Adjungbilly Creek, Messrs. Carroll and Gillespie are working the Mount Mary Mine on tribute from Mr. Quilter, in whose property it occurs. About 400 tons have been dispatched to Sydney, averaging, according to the tri-butors, from 48 to 49 per cent.

The main bunch, which underlays to the west, has been worked hitherto in a most dangerous open cut, about 45ft to 50ft long and from 20ft to 30ft deep. The ore body under foot is solid, and about 7ft thick, whilst a wedge of ore remains in the upper work-ings 12ft high and. 10ft broad.

Evidently a considerable amount of ore is still available when a proper system of extraction is adopted.

Several smaller bunches have been more or less exposed by open cuts and shallow shafts higher up the slope of the mountain. In one instance, a thickness of about 1ft 6in is exposed in a shallow shaft.

The most important of the new finds, however, has been found near the top of the ridge, where the soil has been removed for a small space, partly exposing an outcrop of solid ore for about 10ft by 4ft.

Fifty feet south another small bunch occurs, which may prove to be connected with the former, but no attempt has been made to uncover the entire out-crop, notwithstanding that a considerable expenditure has been decided upon in the construction of a tramway to convey the ore from the deposit to the northern foot of Mt. Lightning, a distance of about 50 Chains.

Sufficient fall is stated to be obtainable through a gap to enable the loaded trucks to run by gravity to the foot of the ridge, whence the ore will have to be carted to the river and conveyed across by cable or other means.

The empty trucks will be returned by horse traction.

The impetus received in the descent of the ridge, however, should be sufficient to carry the loaded trucks to the river side as the falling ground continues to within a very short distance of it.

On the west side of the continuation of the serpentine ridge, south of Adjunbilly Creek, in portion 173, Messrs. Welch and party extracted 220 tons from a deposit, which unfortunately appears to have pinched out entirely in the bottom of the open workings.

On Mr. Robert Owen's property, in addition to the Kangaroo Mine, Messrs. Gimney and Thornycroft are engaged prospecting on behalf of Mr. Joseph Edwards, of Katoomba.

So far, 12 deposits have been opened which yielded 1800 bags of ore, about 75 tons. The grade in several in-stances is stated to have been very close to the minimum.

Four known bunches have yet to be proved.

The largest yet found by the prospect yielded about 21 tons.

The Kangaroo Mine is situated in portion 128, parish Wagara, county Buccleugh.

The proprietor, Mr. M. Constable, holds two leases of 80a and 40a, subject to terms agreed upon with the owner of the land.

About 1230 tons of ore have been dis-patched to date (8|2| 95) the output of late being at the rate of 100 tons per week.

The ore body has been proved horizontally for about 200ft by two open cuts following the irregularity of its contour.

The Strike is a little west of north and the underlay west.

The ore body was originally narrow at surface (as I am informed),but open to about 18ft in widest parts

in sinking. At the present lowest stope at the north end about 6ft of solid ore is exposed; and at the south end (of main opening) about 5ft is showing without reaching the hanging, wall, which at this point is undercut by the swelling of the ore body.

In the bottom there is a length of 54ft by an average width of about 4ft of solid ore.

At the surface at the extreme south end of the main opening the ore bunch seems to be divided by a block of country.

The quality of the ore in the Kangaroo Mine has so far proved consistently good, as may be judged from Mr, Constable's statement that, as regards the 1230 tons dispatched, the lowest average in the account sales of any consignment was 53 per cent. and the highest 57 per cent.

The second bunch of chromite occurs a few feet above Brungle Creek, and close alongside the Tumut-Tomorrowmah road.

Here an opening has been made in the north-western side of the above-mentioned spur, in which about 6ft by 3ft of solid chromite has been exposed under foot, the longest axis having a north and south direction, which corresponds pretty close-ly with the side of the ridge from this point.

At the Kangaroo Mine the following method of preparing the ore for market is adopted:-

The ore as it comes to the dressing floors from the mine is divided into "firsts" (clear ore), and "seconds" (mixed ore and country).

The "firsts" ore is broken into pieces about 3in in diameter, and filled into bags direct. The "seconds" ore and country is broken by hand, and picked, the residue being screened and again picked.

The filled bags average about 24 to the ton. At least, one-sixth of the ore is lost as "smalls"- a loss which might pay to obviate where water is plentiful, by use of coarse jiggs, or possible by box head sluices.

A trial with one of the latter set at a high angle would prove whether the fragments of serpentine rocks could be removed by sluicing. Specific gravities of chromite and serpentine being 4.3-5 and 2.5-7 respectively.

I am indebted to Mr. M. Constable for the following statement of price obtainable for chromite delivered in Sydney, viz., 70s per ton for 50 per cent., and 2s 6d per unit over that percentage.

It is difficult to ascertain the lowest saleable grade, as buyers fight shy of ore yielding less than 48 per cent, of sesquioxide of chromium; and much prefer not to deal with ore carrying less than 50 per cent.

The fall in the value per unit below 50 per cent, is very rapid.

The cost of carriage by team in the Gundagai district has so far averaged from 10d to 1s per ton per mile.

Railway freight depends upon the extent of the consignments, the following being the ruling rates:- Ore in 120 tons, Gundagai to Sydney, 13s per ton; next 60 tons, Gundagai to Sydney, 12s per ton; over 180 tons, Gundagai to Sydney, 11s per ton (minimum rate).

The ship-ping rates do not come into consideration as the price quoted is for delivery in Sydney, where the chief buyers are Messrs. Dalgety and Company and Gibbs, Bright, and Company.

The following figures represent the approximate yields from the different mines to date, February 10, 1895:- Kangaroo Mine, 1230 tons; Vulcan Mine, 1200 tons; Quilter's Mine, 1100 tons; Mount Mary Mine, 600 tons; Welch's Mine, 220 tons; Zigzag Mine, 100 tons; J. Edwards's Mine, 75 tons: total, 4525 tons.

According to the literature of the subject, the chief chrome supply of the world appears to be drawn from Asia Minor.

America obtains about half her acquirements from the State of California, where, according to the State mineralogist's twelfth annual report, 1894, pp. 35, 36, 37, "ores producing less than 50 per cent, cannot be handled and shipped to compete with those from the Mediterranean.

Owing to the 'pockety' nature of the deposits, it is difficult to determine anything about their extent, except by actual work, and the deposits or pockets are usually soon exhausted.

The bunches and connecting stringers are arranged in such an exceedingly irregular manner that no rule can be laid down for tracing the ore bodies."

In connection with the chrome industry in the Gundagai and Tumut districts, the feeling of uncertainty which now prevails as to the permanency of the deposits, consequent upon the rapid exhaustion of several promising-looking bunches, is aggravated by the method off mining adopted, viz., open cut, which reveals nothing until the bottom drops out of the mine.

Where the bunches are small such a sys-tem is the only one necessary and possible; but when the deposits afford indications of extent systematic prospecting by shafts and drives should be adopted at the outset to determine the vertical and horizontal extent in each case.

The prosecution of such necessary testing would not only set at rest any uncertainty on the score of extent, but also afford an immediate supply of ore for dispatch, and enable further operations to be regulated strictly in accordance with the amount avail-able.

Chrome mining in the districts in question has now been advanced to a stage which enable a fairly clear opinion of the nature and mode of occurrence of the deposits and the experience of the past year teaches that they in no way differ from those of other countries, which have been described as "pockety" and "bunchy," "irregular" and "uncertain."

Therefore, it seems imperative if the chrome industry is to be advanced and maintained as a profitable commercial undertaking, that systematic prospecting must be kept well ahead not only of actual winning, but also of actual discovery, so that new finds may be made available as the old give out, and thus prevent frequent cessation of work.

With resolute grasping of the fact of comparatively small. but numerous and widespread deposits, coupled with systematic prospecting and proving, careful blending of ores and uniformity of grade, and by saving and concentration of "smalls" where practicable, there can be no doubt that the chrome industry of the colony will be maintained on a vigorous and profitable scale.

In addition to the localities mentioned in my first report, chrome deposits have been found in the serpentine country lying

between Attunga and Manilla, and are probably connected with those nearer Barraba. Samples from several deposits have, however, proved, of low grade. A chrome bunch was also opened by Mr. G. S. M'Glew on an M.L. of forty acres, about three miles south east of Moonbi Railway Station, but it soon gave out.