Shafts

There are three main shafts, 400, 500 and 115 feet deep, respectively.

No. 1 shaft is 401 feet deep, is sunk on distinct vein, has five levels, work has been done on three distinct veins, varying in width from 8 to 50 feet, and there has been drifted upon these for a total of over 1,500 feet.

The values of the different ore shoots range from $3 to $14 per ton, average as mined and sent to mill $5 per ton.

No. 3 shaft is about 500 feet deep, is sunk on No. 3 vein near its junction with no. 4 vein; there are five levels in this shaft; work has been done on four distinct veins, varying from 6 to 35 feet wide, and these have been drifted upon for a total of over 2,200 feet.

No. 3 shaft is 1,200 feet east from no. 1 shaft; when work was started here it was supposed to be on the same vein as no. 1, but the writer has good reason for believing that these two shafts are on different veins, the general make-up of the vein filling is not the same, and the strike as found by surveying indicates that there are two veins more or less parallel and the discovery of a vein north of shaft on 500-foot level serves to confirm this.

Where No. 3 and No. 4 vein join on first level, they form from here down, a large chimney of ore, 25 to 35 feet wide. This has been mined to third level, giving a large tonnage of ore, which averaged over $6 per ton, and this chimney will, no doubt, continue to depth.

Similar conditions were found at the junction of No. 3 vein, with a vein joining it from the northwest, making an ore-body in placed 40 feet wide, which has been mined to 200-foot level and will, no doubt, continue to depth.

The ore of the different veins worked through No. 3 shaft show higher values generally than No. 1 shaft. There are ore shoots in this shaft ranging from $8 to $14, and even as high as $60 to $80 per ton, in places.

The drawing illustrates the last 100 feet sunk in No. 3 shaft. The vein varied from 7 to 15 feet wide, was sampled regularly and shows an average value of $6.34 per ton.

Besides the main workings as above described, there are several others which the present company have not worked on.

The following descriptions are from the records:

• No. 7 shaft is 115 feet deep. This is sunk on one of the spur veins, has one level, 195 feet long.
• No. 7 vein is very uniform in width: that is 7 to 8 feet. The ore extracted from this vein averaged over $7 per ton.
• No. 4 has shaft 34 feet deep, an adit level 120 fee3t long, vein 4 to 5 feet wide.
• No. 5 shaft, 105 feet deep, sunk on No. 5 vein, which is from 12 to 40 feet wide, has been drifted on for 178 feet.
• No. 5A shaft, 95 feet deep on same vein, no drifting.
• No. 6 shaft is on No. 6 vein, is 80 feet deep, one level 80 feet long, 6 to 8 feet width of vein.
• No. 10 shaft, 126 feet deep, sunk on No. 10 vein, has one drift 81 feet long; crosscut has shown this vein to be 42 feet wide in places
• No. 8, 9, 11, 12 veins have received no attention, as yet, other than general inspection to ascertain their widgh and value where opened on, they vary from 12 to 40 feet wide and the values from trace to $12 per ton.

Ore Available

There is about 12,000 tons of broken ore on the stulls in No. 1 and No. 3 shafts, and a further 70,000 to 80,000 tons readily available. The work in progress, is to sink No. 1 shaft to 500 feet, same level as No. 3 shaft, and connect these two shafts by level at 500 feet. Shis will develop on main vein and spurs from 600,000 to 1,000,000 tons of ore at a cost not to exceed 25 cents per ton and the mine will then be ready for a daily output of 1,000 tons.

Ore Reserves

It may safely be said about Cordova Mines that prospective ore reserves are unlimited. There are 15 known veins, some of them traceable for over one mile, and it will be conservative to state that these veins average 10 feet wide.

To give an illustration: If we take but one vein, allowing that is it 5,000 feet in length, average 10 feet wide, and extends to 1,000 feet in depth, we will have 10,500,000 tons, enough to make a big mine in itself, even if cut in half and only having one such vein.

If we allow that we have at least three veins that might be figured on for 5,000 feet in length and 3,000 feet in depth, we are dealing with immense tonnage, namely, over 30,000,000 tons.

The writer is of the opinion that these results may confidently be expected, basing his judgment on what has been learned from development to date.

It is not necessary to say anything further on this subject, although the writer is of the opinion that this property will exceed even the above estimates.

Summary

The work done up to the present has been largely confined to the main vein system, through work done in No. 1 and No. 3 shafts, the greatest depth attained to only 500 feet. The ore deposits at Cordova may be safely counted upon to extend to great depth, as deep as it will be found economic to follow them.

With the knowledge acquired through the work done there can be no doubt about the permanency of these veins. There has been all told, some 70,000 tons of ore extracted and milled, producing in round figures $330,000.00 in gold, the records of the former company show that 70 to 80 cents per ton was lost in tailing, the milling done by present company has reduced this loss to less than 50 cents per ton; but, taking the average at 50 cents per ton lost in tailing, it will be seen that the ore extracted has averaged over $5 per ton.

A number of tests have been made recently, demonstrating that the mill will crush 100 tons per day and extract over 90 per cent, of assay value, furthermore, that by slight changes and addition of tube mills, etc., the capacity will be brought up to 200 tons per day and recover will be 95 per cent, of assay value.

It has also been fully demonstrated that total cost of mining and milling, including overhead charges, will not exceed $2.50 per ton.

It is, therefore, safe to estimate that with a daily capacity of 200 tons the following results should be obtained:

200 tons per day, average value $5 per ton: —

With the mine further developed as above to 1,000 tons daily capacity, it can be safely estimated that the cost will be brought down to $2 per ton and the following results should be obtained: ——–

1,000 tons per day, average value $5 per ton : ——

The work already done on the main vein system and what is known of the other veins on the property fully justifies making the above estimates.

The mine can be brought up to 200 tons daily capacity in six months’ time and to 1,000 tons daily capacity one year later, and even this latter can be doubled or even quadrupled in time, simply a question of development and equipment and as far as can be judged it will take 50 years or more to exhaust the now apparent ore reserves.

P. Kirkegaard,
Mining Engineer