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50 per cent. extractable, indicates a workable reserve of the order of 50 million 49ng f. 6The reserves of stoneware daygeares af 602excess of this figure.
NORTH DEVONwumtojob
66. The low-lying tract of the Mere Valley between Peters Marland, Meeth and Petrockstow contains workable clays over a length of 44 miles by 2 mile wide, i.e., about 33 sq. miles. The beds are in a basin and in places plunge steeply, especially on the N.E. margin, flattening out in the central areas. These clays have been worked since the middle of the 18th century.
67. The reserves of whiteware and stoneware clays are probably com- paratively large, as in the two localities which are being worked borings have proved the presence of several workable beds at shallow depths. In general the north Devon whiteware clays tend to be more siliceous than those of south Devon and Dorset.Jte
DORSET
te tine
68. Plastic clays have been worked in the neighbourhood of Wareham and Poole Harbour for over two centuries, the latter district being especially noted for its “pipe-clays" where sections of the main bed have a thickness upwards of 25 ft.
off
69. Annual outputs for many years past have been over 100,000 tons, and the proved reserves of clay exceed 4 million tons, whilst the probable reserves are very much greater; for example there are strong grounds for belief that an area west of Corfe Castle, at present requisitioned by the War Office, contains reserves perhaps amounting to 10 million tons.
Summary
70. The reserves of the most valuable whiteware clays probably exceed all predictable home and export trade requirements for as much as 50 years. Those of stoneware clays are probably even greater. It should be noted, however, that these are estimates based mainly on indications only and that the reserves cannot be considered proved in the accepted mining sense. Having regard to the variability of the beds, both in thickness and extent in certain areas, and other complicating geological factors, there would seem to be every reason to seek confirmation of the extent of the indi- cated reserves by boring or other means. In particular, further informa- tion should be obtained about the exact distribution of the deposits in order that, where necessary, working could be planned on a long-term basis.
BARIUM BRINES ·
;
71. The presence of barium chloride in the waters encountered in some of the collieries in S.E. Northumberland and adjacent parts of Durham, has long been known, but their economic exploitation is confined to the Backworth Colliery of the Northern Division of the National Coal Board situated about 10 miles N.E. of Newcastle-on-Tyne.
72. At this colliery a portion of the mine waters carry 0.7 per cent. barium chloride in addition to 6 per cent. of sodium chloride and a small amount of calcium chloride. They are pumped from the lowest level of the pit to surface storage tanks, from which they are drawn off, filtered and treated with sulphuric acid when barium sulphate is precipitated and hydrochloric acid fgenerated; this acid is then employed tp3convo purchased witherite into additional barium chloride for the sulphate reaction.
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73. This process at the present time is being operated to yield an annual
total of processons of high-grade precipitated banga 4ulphate blanc
fixe), two-thirds by direct conversion of the brine salt and one-third roughly from the resultant hydrochloric acid reaction with witherite.
Summary
74. The economic merits of this process warrant its application where similar mine waters occur, for which purpose we agree that steps should be taken to carry out a detailed survey of the occurrence of such waters in this area, and an estimation of their volume and precise mineral content.
B: Dogber on Yar song or a estant br
Occurrence #TER
BARYTES
75. The mineral barytes, known also as barite (BaSO), has been found in economic quantities in veins in the Northern Pennines, the Durham Coalfield, Devonshire, the Lake District, Derbyshire, Shropshire, North and Central Wales and Somerset. Present production comes mainly from mines situated in the first four mentioned districts although a considerable quantity of second grade product is recovered in Derbyshire from old lead-mining dumps. Barytes, like fluorspar, is often associated as a "gangue” mineral with lead and zinc ores.
76. For information on the geology of barytes occurrences in England and Wales we have relied mainly upon a recent publication of H.M. Geological Survey.*
Uses
77. When barytes has been freed from impurities and finely ground, its industrial uses depend upon one or more of three properties, namely chemical inertness, white colour and high specific gravity.
gravity. Its main use is as an extender in paint, and as a filler for linoleum, rubber, paper and textiles. Off-colour barytes is used to make up heavy mud in oil well drilling and a heavy medium for the sink-and-float type of coal washing process. Barytes has also important chemical uses, the chief of which is as a raw material for the preparation of blanc fixe and lithopone and in certain titanium pigments used in the paint industry.
Production
78. The commercial importance of barytes became recognised in the latter half of the last century. From about 1860 to 1900 production in the United Kingdom averaged 20,000 tons per annum which satisfied domestic requirements. Thereafter both production and demand expanded rapidly and in the 20 years preceding 1939 figures for which averaged 50,000 tons and 90,000 tons per annum respectively, the balance of demand was met by imports. During the 1939-45 War, when imports practically ceased, pro- duction was expanded to about 90,000 tons per annum which satisfied essential demands. Production has since dropped to about 80,000 tons per annum. Imports have recommenced and exceeded 15,000 tons of ground and unground mineral in 1947.
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Barium Minerals in England and Wales" Wartime Pamphlet No. 46, Geological Survey and Museum, 1945.