bitumen, barite, fluorspar, etc. One dollar is deducted for each per cent of iron above 1 per cent. The first ore sold from the new Miami district was penalized 2 "per cent," that is, $2 was arbitrarily deducted for the bitumen clinging to the concentrates. The blende concentrates from Miami average about 50 per cent zinc and are penalized $10 per ton for falling 10 "per cent" below the "base," as well as an additional penalty for the iron contents. In practice, however, it has been found that these penalties are heavier than necessary and the ore buyers offset the excess by increasing the base offer over the base price obtaining in the other parts of the Joplin region where the concentrates average nearer 60 per cent. Fluorspar occurs in the zinc concentrates of western Kentucky and southern Illinois, but neither fluorite nor barite are found in quantity in the ores in the Joplin or the upper Mississippi Valley districts. The practice of buying zinc blende concentrates on an assay basis became general in 1899, though it began in a small way a few years earlier. Formerly the ore was bought on "flat bid;" that is to say, the buyer made a visual inspection and mental estimate of the metallic contents and then offered so much per ton for the particular concentrates in question. An expert buyer can estimate the metallic contents very closely. Galena concentrates are generally bought on flat bid, though buying on assay is increasing. Ore which is sold in lump, such as hand-picked galena, lead carbonate, and carbonate and silicate of zinc, is very generally sold on flat bid.

ASSAYS.

Several of the assayers in the Joplin district make a practice of saving the remnants of samples analyzed through the year. At the close of the year the lot is thoroughly mixed and carefully sampled, from which sample an average or composite assay for the year is made. Two representative series of such composite assays are given below. In most cases each sample included in the composite assay represents a carload lot of concentrates.

The first series, by W. W. Petraeus, of Joplin, gives the result of analyses of composite samples from the general district for the last twelve years. The analyses for 1897-1905, inclusive, were published in the Lead and Zinc News, volume 9, January 15, 1906, page 8. The analyses for 1906-1909, were kindly communicated by Mr. Petraeus. Iron was not taken into account until 1900. Some 400 scattering assays, made in 1895-96, are excluded from the table.

Composite assays of zinc blende from the Joplin region, 1897–1908.

The composite sample for 1905 also assayed: Lead, 1 per cent; copper, 0.001 per cent; cadmium, 0.198 per cent.

The next series of composite assays was communicated by Prof. W. George Waring, of Webb City. The original samples were of ores from the different camps of the district except where otherwise indicated. The methods used in making these assays have been published."

Composite assays of zinc blende from the Joplin region, 1900-1908

The complete analysis of the composite sample of the 3,800 lots of concentrate from the Joplin district in 1904, sampled by C. V. Millar and analyzed by Waring, is as follows:

Analysis of composite sample of zinc blende from the Joplin region.

Both series of composite assays show a slight but gradual increase in the zinc content of the concentrates from the beginning of the series to the present time. The second series indicates a similar decrease in the quantity of iron. Both these changes are doubtless to be attributed to the increased efficiency of mills and milling practice, particularly in the sheet-ground districts. The first series shows indications of a lowering of the grade of concentrates by the custommill product of the gougers and scrappers in the latter part of 1907 and in 1908, while many of the large mines were shut down because of the low price of ore.

a Waring, W. George. The volumetric determination of zinc, Jour. Am. Chem. Soc., vol. 26, No. 1, January, 1904. In addition to the composite assays for 1902 and 1903, shown in the table, the article gives the lead, copper, and cadmium content of a number of ores from individual mines in Missouri, Kentucky, and Illinois.

PRICES.

The two charts following show graphically for the years 1908 and 1909 the average price of spelter at St. Louis, the weekly average basis price of 60 per cent zinc concentrates at Joplin, and the weekly production of zinc blende in short tons by the Joplin region as a whole. The price of spelter has been taken from market reports, and the price of zinc blende and the figures of weekly production are those published in the Joplin Globe and the Joplin News-Herald. The sharp weekly fluctuations in production result from the holding back one week for better prices and the heavy selling when prices are higher. The curve, strictly speaking, is that of sales, but throughout this report only that ore which has been marketed is considered in the production. To eliminate these weekly fluctuations and to obtain a curve more easily comparable with the price curves, the weekly sales have been averaged by months, the result being shown by the broken line.

In the main the price of zinc blende closely follows that of spelter, the margin between them being naturally smaller as the price of each falls. Some discrepancies appear here and there, in part the result of scarcity of ore owing to inclement weather, breakage of naturalgas mains, holidays, etc., and in part the result of tariff agitation. Likewise the weekly production bears a close relation to the price fluctuations, especially as shown in the curve of weekly production averaged by months. This relation is somewhat counteracted, however, by the law of supply and demand, high prices resulting from a scarcity of ore, and vice versa.

CENTRAL AND SOUTHEAST MISSOURI.

The ore deposits of central and southeast Missouri reach in a more or less connected belt from the region of Morgan, Moniteau, Cole, and Miller counties on the northwest to the northern and eastern flanks of the St. Francis Mountains on the southeast.

The deposits in the northwestern portion of this belt, corresponding to the central Missouri region, are of the general type of those in the Joplin region, in that the ores consist of galena and sphalerite, or the oxidized derivatives of those minerals, and occur in association with solution breccias and sink-hole shale patches, the ore being found in the Cambrian and Ordovician dolomites and included cherts and occasionally in the shale. The occurrence of ore in crevices or thin vertical sheets is very common, but practically all the production of ore has been from sink-hole breccias or "circles," a form of deposit noted also as important in the southwest Missouri area.

The southeastern part of the belt, in the vicinity of the St. Francis Mountains, forms the disseminated lead region of southeast Missouri. The ore in this region is almost wholly lead, though a considerable deposit of zinc ore occurs at Valle Mines, some 6 miles north of the Bonneterre district, and furthermore copper, nickel, and cobalt ores occur with the lead in the vicinity of Fredericktown in the southeastern portion of the region. The lead ore generally carries some silver, the average being less than 2 troy ounces to the ton of lead concentrates. The ore deposits are almost wholly in the lower part of the Bonneterre limestone, where they occur in disseminated form over large areas, relatively richer in the vicinity of the intersecting

$ 0.050

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC
41831842

Average base price per ton for 60 per cent zinc concentrates at Joplin

30.00 TONS

30.00

7000

FIGURE 1.-Average weekly prices of spelter and of 60 per cent zinc concentrates, and weekly production of zinc concentrates in the Joplin region in 1908.

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC

FIGURE 2.-Average weekly prices of spelter and of 60 per cent zinc concentrates, and weekly production of zinc concentrates in the Joplin region in 1909.

crevices and joints. The crevices show little if any displacement, and there are no breccias of consequence. The copper, nickel, and cobalt ores occur with galena and marcasite in blanket formation in the carbonaceous beds of parting at the contact of the Bonneterre limestone with the Lamotte sandstone below, and in the vicinity of the intersection of this contact with the sloping surface of the pre-Cambrian rocks. Both the Bonneterre and the Lamotte formations are of Cambrian age.

The southeast Missouri deposits have been known and worked for about two hundred years. The earlier workings were shallow and even yet considerable shallow lead is raised, generally in connection with the mining of barytes, or "tiff," as it is locally known. The mines in the disseminated lead region range from 100 feet to about 550 feet in depth, depending on the depth from the surface to the basal portion of the Bonneterre limestone. Prospecting is done by means of the diamond drill, and extensive campaigns of drilling have been prosecuted in the vicinity of all the important producing tracts. The silver production of southeast Missouri was 14,188 fine ounces in 1909, and 49,131 ounces in 1908. The production for 1909 was recovered from about 31,000 tons of lead concentrates and that for 1908 was recovered from 26,488 tons of lead concentrates, each quantity representing less than 15 per cent of the total production of lead concentrates for the respective year. The remaining 85 per cent of the concentrates from southeast Missouri was not desilverized. As explained already the quantity of silver produced during any year bears no direct ratio to the quantity of silver-bearing lead concentrates smelted during that year, for the reason that the silver bullion is stored and refined in batches at convenient times. In a series of years the silver content of the concentrates appears to average about 1 fine ounces to the ton.

The mines of the disseminated lead district of southeast Missouri remain very much as described in Mineral Resources for 1908. In Madison County financial difficulties overtook the Madison Lead and Land Company, which was declared bankrupt and ordered sold under foreclosure proceedings. The Eastern Lead Company, succeeding the defunct Hudson Valley Lead Company, went under foreclosure as a preliminary to clear the way for reorganization.