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May, 1944

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There are very large reserves of iron ores and ironstones in Great Britain. To quote from J. D. Kendall's classical work, "The Iron Ores of Great Britain and Ireland":

Although the hey-day of some of the great mining areas seems to be past, new fields have come into prominence, and the pre-war output of British ores of 14½ million tons is now well exceeded.

Actual figures of reserves vary tremendously from different sources, but probably the figures in Table I, given by Charles Hart, give an idea of the ore reserves of Great Britain in 1922 :

Numerous subdivisions of these main sources have been given, but the above show how considerable are our reserves.

Table II gives the outputs of ironstone from the various sources of supply, whilst Table III gives the geological chronology of the various iron ores and Table IV gives a chemical analysis of the most important ores. Fig. 1, showing diagrammatically the world production of iron ore, is an average for the four years 1935 to 1938.

A study of the geological and mining aspects of these ores can be conveniently divided into two main sections. These are the unstratified deposits and the stratified ones.

Unstratified deposits

Cornwall. Though Cornwall is, and always has been, generally associated with " fish, tin and copper," it has considerable iron ore reserves.

These ores are in the form of " lodes," and are usually near the surface in the carbonate zone, having a maximum depth of about 400 ft. At greater depths these iron lodes often change to copper and/or tin lodes. In July, 1939, the then President of the Cornish Institute of Engineers said, "It is very likely that the Great Perran Iron Lode may indeed prove to be far more important as a copper or even a tin lode in depth than as an actual iron deposit." And he went on to say that if it were so, then it would only be a case of history repeating itself.

In a recent review of the iron deposits of the West of England, F. J. Stevens gives an interesting historical review of iron mining in Cornwall. Former mining areas are near St. Just and St. Ives, in the Lizard, Meneage and Perranporth districts and the St. Austell and Bodmin areas. The zenith of these mines appears to have been about 1860 to 1870 and most mines were closed by 1880. Isolated mines struggled on against poor prices and other difficulties for instance, the Restormel mine in the St. Austell area carried on spasmodically until 1912.

As far as we know, there has only been one revival in recent years. Early in 1939 the Great Perran lode was reopened for working on a large scale and was still being worked last year. The ore is good quality brown hematite changing to rich carbonate in depth. It was decided to work the iron ore lode by opencast methods down to water level, about 150 ft., since pumping to this depth would not be necessary. Initially, the overburden between the two old quarries worked in the latter part of the last century was removed by a 12 cu. yd. capacity American trac-tractor pulled by a 100 h.p. diesel engine. The proposal was then to dig and load the ore by the same machine after the ore had been shattered by blasting with low density explosives. Incidentally, this scraper outfit removed 40,000 tons of overburden in the first six weeks that it was operating.

Iron mining in Cornwall has never produced large tonnages. Difficulties have been numerous. The geology is complex, the ores very variegated and interspersed with other ores, and often contaminated with minerals which are difficult to extract later in smelting. In addition, there have been numerous mining difficulties due principally to water. All these have resulted in a decaying industry in so rich a mineral area of our island; this applies to Cornish minerals in general. It may have a future if the capital and initiative are available and in years to come we may see Cornwall a hive of mining industry once more.

Devon. There are very many deposits of very many types. The Upton Pyne manganese deposits were once of great importance, as were the magnetite deposits of the Maytor mine. Bovey Tracey iron lode gave a micaceous iron ore known as "Devonshire Sand," and the Brixham mines gave a soft red hematite called "Paint ore." All is derelict now and it is most unlikely that there will be any revival. Somerset. There are numerous iron lodes in the Brendon Hills, and these were worked quite considerably between 1845 and 1875 ; in the latter year there were 13 shafts extending for nearly four miles. Traces of hematite have been found in the Mendips.

Forest of Dean. Iron ores, mostly limonites, have been worked in the Forest of Dean since Roman times. During the last war there was a considerable revival, but at the moment there are only two small mines working. Most of the mines have been closed for more than 40 years. The ore is very variable and shows an iron content of from 15 to 65 per cent. Dr. Sibley suggested that the ore deposits decrease in depth and the source of iron was from the triassic mantle above. It is very probable that most of the mines were nearing exhaustion when abandoned. The ore field can be divided into an eastern district and a western district.

The most productive area of the eastern district is southwards from the Wilderness near Mitcheldean to Soudley. Ore has been won at three mines — Edgehill, Shakemantle, and Perseverance. Edgehill was worked from four levels, having a total drivage of 23,000 ft. before it was abandoned and left flooded in 1893. It was in continuous operation from 1843 to 1893 and produced 958,000 tons of ore in that time. Shakemantle had four shafts and numerous levels and the total drivage was very great. It was abandoned in 1899. Perseverance had two shafts and numerous levels. It also was abandoned in 1899. Mining methods varied very largely since these deposits were most irregular but consisted of driving levels in the limestone (Crease limestone or Whitehead limestone) and then using stoping or pillaring methods.

The western district comprised the Staunton area, the Coleford area, Tufton to Clements Tump area, Clements Tump to Bream area and the Bream to Lydney Park area.

In the Staunton area were the Staunton pit, which worked from 1865 to 1873 and produced 13,000 tons, and the Robin Hood mine, which worked small veins and pockets till 1927. There is still some unexplored ground in the Crowsnest mine, which produced 44,000 tons.

(To be continued.)

Drawings and Photographs accompanying the article