tion to wagons than upon the actual distance of the mines from Placerville. At Long Park very little ore has to be packed and most of it can be loaded directly on the wagons, the cost of hauling to Placerville being $20 per ton. Saucer Basin has to stand this charge for hauling and in addition a pack rate of $8 to $10 per ton. It is somewhat difficult to find out the exact cost of packing the ore on burros, as many of the companies own their own animals, but the figures here given may be considered approximately correct. From the East Paradox mines of the Standard Chemical Co. and the General Vanadium Co. the cost of hauling is $18 per ton; in addition the ore has to be packed down the mountain side at a cost of probably $2 or $3 per ton. From Bull Canyon the cost of hauling is at present $20 per ton, with a pack rate of $5 per ton. This figure will probably be reduced slightly after the completion of a road that is being built. The freight rate from Placerville to New York is $11.57 per ton, and from Placerville to Hamburg or Liverpool, via Galveston, $14.50 per ton. The average cost of transportation of the ore is, therefore, $29.57 to $42.50 per ton. In the case of some of the outlying districts the cost per ton is even more than the higher figure. Adding to this an average cost of $34 per ton for mining, sorting, and sacking, the total cost to the operator is from $63.57 to $76.50 per ton. This does not include costs of powder, tools, assayer's charges, etc.

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Up to the present time there has been a ready market for ore containing 2 per cent U2O, or more. Most of the purchasing agents have refused to take any ore of a lower uranium content, although a small quantity of ore has been sold during the past year containing 1.7 or 1.8 per cent. All ore is bought on the basis of its uranium content, a high-grade vanadium ore being difficult to sell if it contains less than 2 per cent UO,. This is one of the unfortunate features of the present mining conditions, much vanadium ore carrying a little uranium being left on the dump and in the mine. One carload of ore that contained 8 per cent V2O, but only 1 per cent U2O, was held up indefinitely. If this ore had carried 2 per cent UO, and less than 3 per cent V2O, it could have been readily sold. The ore is purchased for the radium that it contains and not for the uranium and vanadium, which are considered as by-products. The foreign buyers established the 2 per cent minimum for uranium and seem to be indifferent to the percentage of vanadium in an ore.

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The prices paid for ore vary within narrow limits. One agent offers for 2 per cent U2O, ore $1.30 per pound of uranium oxide; for 21 per cent ore, $1.40; and for 3 per cent ore, $1.50. For the V2O, content he pays $0.30 per pound. These prices are f. o. b. New York. An operator who has received offers from several agents states that the prices quoted vary from $1.25 to $1.40 per pound of uranium oxide for 2 per cent ore and $0.35 per pound of vanadium oxide for

ore containing more than 3 per cent of this oxide. Some operators sell their output entirely upon the basis of its uranium content and get nothing for the vanadium. Such a basis usually prevails where the ore is fairly high in uranium and low in vanadium. Where the ore is high in vanadium it is sold for both its vanadium and uranium content according to the prices stated above. When the vanadium is not paid for, the average price given for ore containing 2 per cent U2O, is $2 per pound and for 3 per cent ore $2.25 per pound. Little more is offered for ore containing 3 to 5 per cent U,O,, but for ore containing more than 5 per cent the rate is higher. The high-grade material from "bug holes," carrying 12 to 20 per cent U2O, or more, brings about $3 per pound of the oxide. These prices are all f. o. b. New York or Hamburg.

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Deducting the costs of mining and transportation from these prices leaves a very small profit for 2 per cent U,O, ore. One unfortunate feature of the system of marketing is the fact that much ore passes through the hands of four or five agents before it reaches the final purchaser. With better mining conditions and a lower cost of production, the elimination of some of the middlemen, and with prices for ore based on the fact that radium is the main valuable constituent, the operator should be able not only to get a reasonable profit on 2 per cent ore, but also to realize a small profit on ore containing 11 per cent U2O, especially if it is high in vanadium.

CONCENTRATION OF ORES.

NECESSITY FOR CONCENTRATION.

In the course of investigations of these uranium and vanadium ore deposits it was found that much low-grade ore was left in the mines, and thus lost, and that there was great loss in hand sorting. Since the market demand is for a material containing at least 2 per cent uranium oxide, the miner, that he may ship no ore below this limit, eliminates all ore that in his opinion contains less. As a result much low-grade and also some shipping ore are left in the mine or are thrown on the dump. By concentrating the low-grade ores at or near the mine these wastes can be reduced. There is no doubt that the ores can be concentrated. Tests made on a small scale substantiate this statement.

In concentration by mechanical means the dry as well as the wet method may be used to advantage; the dry method is perhaps preferable, as little or no water is available in many places where these ores occur. Most of the deposits are far from a railroad, so that wagon hauls are long and expensive. By concentration the bulk of low-grade ore to be hauled can be reduced and at the same time the percentage of mineral in the concentrate raised to a marketable point. Thus a

saving in hauling and freight rates is effected, and the concentrate on account of being richer should bring a better price. Low-grade ores thrown on the dump or left in the mine constitute a natural waste. Much of the low-grade material left in the ground during former operations and perhaps much of the dump material can never be recovered. Much of the ore thrown on the dump disintegrates on exposure to the air, so that much of the valuable contents is washed or blown away. Some of the minerals in the dump rock are liable to be leached out by the rain.

WET CONCENTRATION.

The carnotite ores are of great importance, especially on account of their uranium and radium content. Carnotite, which contains both uranium and vanadium, is a yellow, crystalline, pulverulent material, with a specific gravity of 4.136. It occurs in white sandstone as an incrustation on the faces of joints and fractures and is deposited around and between the individual grains of the sandstone, often strongly adhering to the even surface of a grain. The size of these grains varies greatly, but is generally from a little less than 0.1 to 0.2 mm. in diameter.

In concentrating such an ore the rock should be broken and the pieces reduced to about 40 to 80 mesh with crushers or rolls, the crushing being accompanied by rubbing in order to loosen the carnotite from the sand grains. Further attrition should be applied to the 40-mesh material by convenient means. Fine grinding should be avoided, as it produces too much slime.

If the crushed and rubbed material is washed in a revolving tank or trommel provided with a rubbing device, the particles of carnotite that are in suspension can be drawn off after the grains of silica have settled in the tank or cylinder. As some of the carnotite is carried down by mechanical action with the silica in settling, more water should be added and the operation repeated as many times as may be profitable. With such a treatment a large part of the valuable minerals can be extracted.

The slime is washed into settling tanks or other suitable device, and the water after the settling of the slimes can be used over again, as will be necessary in the arid districts, where most of the deposits are located and where water is scarce. Enough water can be collected and stored away for this purpose from seepage, springs, and during rainy days, and in many cases a wet treatment can in this way be made possible.

RESULTS OF WET CONCENTRATION TESTS.

Tests have been made of ore taken from the dumps at various claims. In one instance this ore contained 2.02 per cent U2O, and 2.32 per cent V2O,. Concentration by the wet method gave the following results:

Loss in concentration, 0.7 gram. Concentration ratio=10.156:1. from ore by concentration, V2O=43.035 per cent; U2O=43.08 per cent.

Extraction

Ratio of ore

to concentrate, vanadium content=1:4.275; uranium content=1:4.376. Ratio of radioactivity, measured in the electroscope, ore to concentrate=1:4.56, which shows that the concentrate is 4.56 times more radioactive than the ore.

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Other tests made with ore containing less UО, and V2O, have shown that an extraction can be made with a proportionately similar result.

The

The following result was obtained with a reddish-brown vanadium-bearing sandstone from Utah. The ore was crushed to the size of the grains, rubbed, and then washed in cold water. slimes thus obtained were settled and decanted or filtered. Result of concentration of vanadium-bearing sandstone by wet method.

Concentration ratio=4.72:1. Extraction=66.2 per cent.

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According to electroscopic measurements, and by comparison with a standard material of known U2O, content, it was found that this ore contained approximately 0.71 per cent UO, and the concentrate contained 1.62 per cent.

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In concentrating this vanadic sandstone the content of vanadium was therefore raised to 17.35 per cent V2O, and the concentrate can be sold in competition with the Peruvian patronite. In addition the uranium and the radium can be easily extracted from this ore. Some of the vanadium can not be extracted mechanically; it probably exists in the sandstone as roscoelite, which is bound in the silica.

DRY CONCENTRATION.

Where water is scarce, a dry process can be adopted for low-grade ores. As good concentration with a dry as with a wet process can not be expected, but an equally efficient if not a better extraction can be obtained.

In a dry process the rock should be reduced with crushers and rolls as nearly as possible to the size of the grains of the sandstone. Much of the carnotite can be obtained by sifting the crushed material through a 120 to 150 mesh screen. Care must be taken to collect all

of the dust, as this is richest.

Good results can be obtained by using an air current to blow the finest particles into a dust chamber, in which they are collected. The air current must be steady and evenly expanded, so that the coarse particles will drop out of it, and strong enough to completely lift the material. The coarse material should be carried along with the current for some distance, so that as much as possible of the powdery material can be freed and blown from the coarse grains, which should finally drop without carrying the powder with them. These particles should fall into a discharge spout and thence into bins or other suitable device. The powdery material, which carries the valuable minerals, is collected in dust chambers. These chambers must be perfectly tight. Much valuable mineral has been lost in sampling shipments when the sampling device had no arrangement for saving the dust.

A number of machines that doubtless could be used for the dry separation of these ores are now on the market.

Another method of dry concentration of low-grade ores consists of simple sifting, with previous rubbing, of the crushed ore. The ore is reduced with crushers and rolls to about 40 mesh and is then passed over an oscillating 150-mesh screen. The undersize from the 150-mesh screen is concentrate. The oversize is carried to a device in which the sand grains are subjected to a thorough rubbing, which removes from the silica the adhering fine particles of carnotite.

In the experiment stiff wire brushes rubbing against a steel plate were used with success for the attrition. The entire material was then brought over two screens, one overlying the other; the upper screen being 80 mesh and the lower one 150 mesh. The table below clearly shows what results can be obtained by such a process. The screens must be encased and all of the dust must be collected. The dust from the sifting operation and that which remains in suspension in the dust-proof screen boxes can be blown from these boxes by suitable means into dust chambers and then added to the concentrate.