cite, which is never abundant, and in most of the veins is quite a rarity.

Although most of the veins carry fluorspar steadily for long distances, occasionally as much as several miles, they are sometimes subject to abrupt changes, as in the Slit vein on Peat Hill above Eastgate.

Variations in the type of country rock have not been shown to affect the quality of the spar; the largest bodies generally occur in the limestones, but sandstone strata often yield well, in contrast with the Kentucky deposits, where brecciation and poor yields are the rule at sandstone levels. Shale or "plate " generally has an adverse effect.

Most spar is exported to America and Russia in lumps or gravel form for steel smelting, and the demand for other purposes seems to be quite small. Any grinding is done to extract galena, rather than to produce fluor "sands."

In contrast with Derbyshire, little fluor has ever been recovered from old surface dumps, and now none is so obtained. At one or two mines the vein worked has not been opened before, but access to the spar is facilitated greatly by the work of the old lead miners, who have cut out the central part of the veins where the galena was concentrated and stowed their "gob" or waste, with such fluorspar as they had to remove in their search for lead. Their adits have also unwatered large tracts of ground which can still be worked for fluorspar.

For even an approximate estimate of reserves, abundant data on the rapid variations in the veins would be necessary, but the number of still untouched veins and the relatively small amount of work done on the others create a strong impression that the industry is still in its infancy and that the present output could be greatly increased without danger of exhaustion for a prolonged term of years. The three centers for fluor production in Upper Weardale are now St. John's Chapel, Rookhope, and Stanhope.

NORTHUMBERLAND

Fluorspar is an abundant constituent of the gangue in the old galena mines round Allenheads, a few miles north of the Upper Weardale watershed. Apparently it has never been specially mined there, but there are large quantities on the waste heaps at the mine heads. About 1910 George Blackwell, Sons & Co. had several of these waste heaps hand picked for lump spar, and many thousand tons were taken away and used for fluxing, but a much greater amount remains untouched. The spar is mostly in small blue lump and gravel, and is hard and clear.

Certain layers in these waste heaps consist almost wholly of fluor gravel, evidently taken out when the vein was broad; the upper layers of the heaps, representing the material last thrown out of the mine, usually consist of "plate" and country rock, possibly indicating that the veins pinch in depth.

Spar was hauled 4 miles on a hilly road to Wearfold mine near Surrender. An east-and-west fault has stopped any spar working in the Allenheads district.

YORKSHIRE

In the higher parts of Swaledale and Wensleydale certain veins occasionally carry fluorspar, but nowhere in workable quantity. The spar occurs as nests in the lead veins at Old Rake and South Arngill mines near Muker, where they traverse the Carboniferous limestone. Purple spar has been observed in the Friarfold mine near Surrender, and in an east-and-west fault which follows the course of a fault at Marble Scar near Gunnerside.

In Upper Wensleydale small quantities of yellow fluorspar have been observed at Mossdale Gill.

CUMBERLAND

The Rotherhope mine is operated by the Veille Montague Zinc Co., Nenthead, Alston, and is on each bank of the river opposite Blackburn Bank, 21⁄2 miles south by west from Alston.

The Rotherhope Fell vein, worked from this mine, is a fissure vein trending southwest through Yoredale rocks. It is unusually broad, averaging 15 feet, with 30 feet the maximum, but much of it is shattered country rock set in a matrix of fluorspar, quartz, and calcite, with galena and a little blende. On the northwest flank of Rotherhope Fell the vein can be traced for at least 2 miles, and to the northeast runs across the South Tyne River to join the Dowpot vein. The fluor is of good quality, but is closely intergrown with the other minerals so that pure lump is an exception. The best level for spar is at the Whin Sill under the Single Post limestone at this point; the Scar limestone is also a good producer.

The main adit, opposite Blackburn Bank, is driven 1,200 yards southeast to cut the vein; only 1,500 yards have been proved so far, the intersecting Sir John's vein to the northeast not having yet been reached. The amount of water is not serious, as the average for the whole mine is only about 20 gallons per minute.

A small amount of lump spar is obtained by hand picking after washing, but by far the greatest quantity of fluorspar is produced as a gravel residue from the galena jigs after crushing. It has been

impossible to effect complete separation of the small quantities of quartz, calcite, and blende in the spar.

43

CORN WALL

No fluorspar was being mined for sale in Cornwall in 1916, but the mineral is recognized sparingly in the mining parts of the county, in association mainly with copper ores. According to Rudler, fluorspar is a notable accessory in the lead veins also, especially those near Liskeard. The copper ore is usually replaced in depth by tin ore and wolfram, and the fluorspar usually dies out. Most of the important copper lodes are worked out and the mines abandoned, but fluorspar may be found on many old dumps; near the towns, such as Redruth, it has been picked out and sold to local assayers. All mines are now making wet assays for themselves, and there is therefore no sale for small lots of fluorspar.

At one mine only has any appreciable amount of fluorspar been obtained in recent years. On Hingston Downs near Gunnislake a 20-foot vein of fluorspar was struck in 1906.

Cornwall fluorspar occurs in the following districts: St. Agnes, Lostwithiel, Redruth, Camborne, and Callington (Hingston Downs).

NORTH WALES (FLINTSHIRE)

Fluorspar occasionally accompanies the ores of lead and zinc in the veins that traverse the Carboniferous limestone and Millstone grit of Flintshire, but is nowhere abundant or pure enough to repay extraction.

The Bryngwiog lode at the Halkyn mine yields zinc blende, which, after concentration, contains 10 per cent of fluorspar, but would not repay mining for that spar. The Rhosesmor veins, some east-andwest veins at Pen-y-bryn, and the Coed Cynric vein, about 2 miles southwest of Mold, contain some fluorspar but not in paying quantity.44

SUMMARY

It is interesting to note that in the Derbyshire district the fluorspar is mainly concentrated in the upper 300 or 400 feet of the limestone and that "inward from the margin or in depth the fluorspar is replaced by barytes and calcite." The situation apparently somewhat resembles that in Illinois and western Kentucky.

Much English fluorspar which has been exported to the United States in the past has been of low grade (55 to 75 per cent CaF2) and

43 Rudler, F. N., Handbook to the Collection of Minerals of the British Isles: Mem. Geol. Survey, Great Britain, 1905, p. 86.

Strahan, Aubrey, The Geology of the Neighborhoods of Flint, Mold, and Ruthin: Mem. Geol. Survey, Great Britain, 1890, 242 pp.

high in silica. This grade of material evidently came from the waste piles of Derbyshire. As these dumps are largely exhausted, as the Derbyshire vein material in place is of higher grade, and as quartz is a rarity in the Durham deposits, it is expected that future exports will be of higher grade.

Imported English fluorspar has always sold in the United States at prices much lower than those of domestic spar. In 1914 Burchard 45 stated:

** **

Large quantities of gravel spar produced at a low cost from the tailings of lead mines and from the gob in abandoned mines in England have been shipped to this country as ballast at a very low freight rate. According to American producers spar from England at present competes with American fluorspar as far west as Pittsburgh and practically fixes the market price at that point, while in the Lehigh and Susquehanna Valleys of Pennsylvania and other localities near the Atlantic seaboard English fluorspar can be purchased advantageously. In the latter part of 1913 the cost of imported material, including the duty of $1.50 per ton, was $4.65 as compared with $5.87 for domestic gravel spar. The freight charges on domestic spar to points where it is consumed are generally higher than on foreign spar from the docks to eastern steel plants, so that the differences in cost to the consumer are relatively higher than are indicated.

*

*

This price differential in the past was partly offset by the lower average grade of the imported product. In future the grade will probably be somewhat improved, but the cost will increase, as the product must be obtained by actual mining.

FRANCE

Fluorspar is found in France associated with barytes in the Haute-Loire district, near Langeac, Paulhauget, and Briode. In the Rhone district a vein is known at Vaux-Rebard. Fluorspar is also reported in manganese deposits at Romaniche.

Commercial production of fluorspar in Germany has come chiefly from the South Harz district in Prussia, the upper Palatinate of Bavaria, the Black Forest of Baden, the Thuringian Forest of Thuringia, and Saxony. Statistics of production are available only for Bavaria and Saxony and these are not completely available for all recent years. From 1902 to 1910 it is stated that the annual exports from Germany averaged about 15,000 long tons, and that the total production was probably more than twice this amount.

45 Burchard, E. F., Fluorspar: U. S. Geol. Survey Mineral Resources of the United States for 1913, part 2, 1914, p. 379.

46 Imperial Mining Research Bureau, Great Britain, Fluorspar (1913-1919): 1921, 99 pp. Von Heimrich, Über den Flusspat von Wolsenborg; Ztschr. angew. Chem., Jan. 20, 1920, pp. 20-22. Isser, M. von, Mitteilinger über neu-erschlossene Erzvorkommen in den Alpenlanden: Bergbau u. Hütte, Mar. 15, 1919, pp. 91-98.

In the South Harz district, Prussia, the principal mine is near Stolberg, not far from Nordhausen. The fluorspar occurs in thick veins associated with very small amounts of chalcopyrite, galena, barite, siderite, quartz, and other minerals. There has been a large production from this district, but most of it seems to have been used locally for iron smelting and, to a lesser extent, copper smelting. Formerly it was mostly used in smelting the Mansfield copper ores. No recent production statistics are available.

In the upper Palatinate of Bavaria, fluorspar has been mined in several places, but the most important deposits seem to have been near Wolsendorf between Nabburg and Schwartzenfeld, in northeast Bavaria, east of Amberg. Much of the fluorspar in this district is reported to be low in silica and to contain 95 to 98 per cent CaF2. Fluorspar mixed with barytes occurs in the Thuringian Forest, particularly in the barytes mines of Herges-Voigtei. There are similar occurrences in the Black Forest of Baden.

The distribution of German production by States from 1896 to 1901 is given below. This table is of interest, as it shows the relative importance of the different districts in the past, as well as indicating the total German production.

Production of fluorspar in Germany,1 1896–1901, in metric tons

Most of the German consumption of fluorspar is in the iron and steel industries, but the glass, enamel, and chemical industries are important consumers. In 1921 47 it was stated that, due to the cheapness of extraction and milling and to the condition of German exchange, Germany could export fluorspar with profit at lower prices than any other country could offer. During 1920 Germany exported to the United States 407 short tons of fluorspar, valued at $9,450; in 1924 exports to the United States were 9,924 short tons, valued at $104,189 ($10.50 per ton). Values given are declared values at point of shipment in Germany.

47 Commerce Reports, "Fluorspar industry active in Germany ": U. S. Bureau of For. and Dom. Commerce, Feb. 9, 1921, p. 788.