Lead and zinc ores of Scotland, introduction, historical notes, statistics and the veins

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From: Wilson, G.V. with contibutions by J.S. Flett. The lead, zinc, copper and nickel ores of Scotland. Special Reports on the Mineral Resources of Great Britain Vol. XVII: Edinburgh : HMSO, 1921.
Figure 1. Diagram showing production of Lead and Zinc Ores from Scottish Mines during the years 1850-1920.
Plate 1. Map of Scotland, with Index to one-inch sheets.


Introduction[edit]

Lead ores have a wide distribution in Scotland and, as (Plate 1) shows, veins occur in nearly every county. Many of these have been worked at one time or another, but for the most part only on a small scale and to no great depth, and little is now known of the quality of the ore produced. In many cases these old mines have fallen in, and their sites are now covered up and grassed over so that without reopening them it is impossible to form any reliable estimate of their value.

The principal districts in which lead mining has been actively carried on during the past century are: Strontian and Islay in Argyllshire, Tyndrum in Perthshire, Minnigaff in Kirkcudbrightshire (near Newton Stewart), Leadhills in Lanarkshire and Wanlockhead in Dumfriesshire. Of these, Leadhills and Wanlockhead have produced ore continuously during the whole period. Mining in the other districts named has been in abeyance for a considerable number of years, but owing to new conditions created by the war the old mines at Tyndrum and Newton Stewart are being reopened and trials have also been made on a new vein at Achanarras, in Caithness.

Historical notes[edit]

Metalliferous mining is an old industry in Scotland, and the mining of lead ores was probably carried on on a small scale at different centres at a very early period. The finding of bronze and stone implements[1] in some old surface workings at Leadhills and at Wanlockhead has led to the suggestion that these may date back to pre-Roman times. There is no evidence, however, that the Romans worked lead in Scotland, although a few pigs of Roman lead[2] have occasionally been found. According to Pennant[3] the mines of Islay may have been worked by the Norwegian invaders during their occupation of the country. Probably the earliest authentic record of lead raining refers to the Leadhills district, where in 1239[4] a grant of lands and a lead mine was made to the monks of Newbattle by Sir David Lindsay, and lead ore was sent from there to Rutherglen in 1264.[5] Apparently the amount of lead ore raised in the country was not large, since in 1292 John Comyn,[6] Earl of Buchan, got permission to import lead ore from the Isle of Man. Soon after this lead mines were working in West Argyllshire, and the accounts of the Constable of Tarbert[7] contain an entry of the payment of twelve pence for charcoal and labourers' wages for smelting lead ore. A lead mine was being worked on the confines of the parish of Glenorchy in Argyllshire in 1424, and it is interesting to note that it was declared a Royal Mine[8] under a grant to the King by the Scottish Parliament of all lead mines which yielded more than 1½d. worth of silver to the pound of lead. Soon afterwards this mine was closed down and abandoned.

Up to about the sixteenth century[9] many of the mines seem to have been worked for silver principally, and the lead was often lost during cupellation. Before the end of that century the extraction of silver seems to have become unprofitable and the mines were worked for lead alone. This was often smelted on the spot in shallow hearths, and the silver neglected. In many cases the ore was exported, and the early grants of mines often gave permission to export beyond the seas[10] if through lack of fuel or other lawful occasion the ore could not be properly smelted at home.[11] This export trade was carried on mainly through the Port of Leith,[12] and between 1585 and 1590,[13] 15,717 "stones" of lead ore were shipped for foreign use.

The period from the latter part of the fifteenth to the beginning of the seventeenth century was one of great activity in mining and prospecting, due mainly to the discovery of the gold-bearing gravels of the Leadhills district.[14] At one time as many as 300 men were employed here during the summer months, and gold to the value of £100,000 is said to have been collected in three years. The Treasurer's Accounts[15] contain numerous entries of payments of gold, and also the interesting statement that some of it was used to form the Scottish Crown Regalia in 1542. The richer deposits soon became exhausted, and work ceased when the price of a man's labour exceeded 4d. per diem. During the whole of this period an active search for lead ore seems to have been kept up, and many of the Leadhills and Wanlockhead veins were discovered. In 1593[16] the Leadhills mines were in the hands of Thomas Foullis, who seems to have recognised that the gold-fields were unprofitable, and consequently to have concentrated his energies on the development of the lead mines. By 1597[17] the industry appears to have been in a thriving condition, and the Privy Council issued a proclamation to the effect that any one interfering with the carriers of lead should be severely punished, while the latter were authorised to wear a blazon of lead stamped with the Royal Arms and the private mark of the lessee of the mines.

In 1606 great excitement was caused by the discovery of the silver-lead mine at Hilderstone,[18] near Bathgate. According to report this mine was very productive for a short time and extravagant hopes were raised, but the richer portion soon became exhausted and the mine was abandoned as unprofitable.

A slump in mining enterprise seems to have set in-during the latter half of the seventeenth century, but interest revived with the discovery of the Alva silver mine in 1711[19] For a short time this mine was very profitable, and is said to have returned a monthly yield of £4000 worth of silver. Like Hilderstone it soon became exhausted, and was eventually abandoned. An active search for lead ore was in progress at this time, and resulted in the opening up of mines at Strontian in 1722, and at Tyndrum in 1739. In 1760 this search for lead brought about the discovery of the Glendinning antimony mine, near Langholm.[20] The Black Craig Mine (Newton Stewart) was accidentally discovered in 1763,[21] and soon afterwards other veins were noticed in that district, one of copper ore being found by Leadhills miners on their way through to Blackcraig[22]

From this time to the end of the Napoleonic wars the lead industry appears to have been in an active state, and large quantities of ore were raised. After the signing of peace in 1815 the price of lead fell rapidly from £32 per ton in 1809 to £13 in 1829. Under these conditions several of the mines were closed down, but apparently only temporarily, as between 1840 and 1880 no less than twenty mines were worked for lead ore, including Woodhead, near Carsphairn, which was discovered in 1839. In the early days the ore was practically always smelted locally in shallow hearths, which were often placed in exposed positions so as to take advantage of the prevailing winds, and peat was generally used for fuel. Coal was first used for the purpose in Scotland at Wanlockhead in 1727, and the hearths of that period have by gradual improvements been developed into the present type of Scotch hearths. The Strontian furnaces were built about 1730, and those at Tyndrum in 1768-9.

Many of the small mines appear to have had furnaces of their own, but others apparently were never equipped with smelting appliances, and the ore was often transported either to Holland or to England. These early furnaces were very inefficient, and a large proportion of the lead was lost in the form of waste fumes. Latterly, by the addition of long condensing flues, much of this fume lead was saved. Straight flues, such as those to be seen at Woodhead, were first used, but it was subsequently found that by "zig-zagging" them a much larger proportion of lead could be recovered. Leadhills and Wanlockhead were fitted with this type, but the former were abandoned about 1890, and since that time the Wanlockhead furnaces, together with some in Glasgow, have been the only ones working in Scotland.

The working of zinc ores is a small and recent development of Scottish mining, but a large extraction plant for treating imported ores has recently been erected at Irvine, on the Ayrshire coast.

Statistics[edit]

Output of lead ore[edit]

Few records exist as to the early output of the mines. We find, however, that in 1466, James Lord Hamilton[23] was summoned by the Abbot of Newbattle for removing 1000 "stones" of lead ore from Friar's Moor (Leadhills district), but no information is given as to the time taken to raise the ore. Between 1585 and 1590, 15,717 "stones" of lead were exported from the country,[24] and papers in the Mar and Kellie charter chest[25] give the amount exported in 1614 as 30,000 "stones," which was valued at £20,000 Scots. The old records of the Tyndrum Mines show that 5017 tons of lead were raised there between 1741 and 1768. The Strontian mines seem at one time to have yielded about 400 tons of lead per annum, and Wanlockhead and Leadhills may be said to have each produced an average of 1000 tons of lead per annum for the last 120 years. Definite figures of output exist since 1852, and the following tables, taken from the Mining Statistics issued by the Geological Survey and from the Home Office Reports, give the total output and other information concerning all mines worked from that time to the present day.

Output of lead from Scottish mines during the period 1850-1920

Name of Mine. Periods of Working Lead total output in tons Lead Largest yearly output Tons. Average Price of Lead per Ton. 1800-1919. £ s. d.
Wanlockhead Continuous 87,000 app. 2578 1800-1809 27 14 6
Leadhills Continuoup 85,000 „ 2600 1810-1819 23 6 6
Strontian 1852-1872 1,156 239 1820-1829 29 7 0
Tyndrum 1856-1865 430 94 1830-1839 16 11 0
1840-1849 17 15 7
E. Blackeraig 1854-1881 2,685 341 1850-1859 21 17 5
W. Blackeraig 1853-1872 975 383 1860-1869 20 9 3
Cairnsmore 1853-1860 144 91 1870-1879 20 9 3
Undifferentiated Kirkcudbrightshire Mines 1880-1889 13 8 10
Undifferentiated Kirkcudbrightshire Mines 1853-1859 552 151 1810-1899 11 17 7
Undifferentiated Kirkcudbrightshire Mines 1900-1909 14 6 1
Wood of Cree 1917-1920 6 6 1910-1919 21 10 1
Average price of Lead per Ton
Carsphairn (Woodhead) 1853-1874 867 92
Islay 1862-1882 1436 218
Lossiemouth 1881-1882 6 6
Tomnadashan 1861-1862 1 15 cwt. 1 15 cwt.
Creetown 1866-1868 8 6
Tyndrum 1919-1920 261 4
Tyndrum 1911-1925 339

For fuller details of the prices of lead since 1873 see Home Office Reports, Mines and Quarries, Part III.

Output of zinc ore[edit]

Zinc ore has been worked only on a small scale, and the earliest record is for 1865, when 33 tons of blende were raised at Black Craig Mines (Newton Stewart). From that time till they closed down in 1882 a fairly constant but small output of ore was kept up. In 1871, 30 tons of blende were mined at Corrantee (Strontian).

Prior to 1880 the blende was not saved at Wanlockhead and the slimes were allowed to run to waste. In that year, however, 39 tons were produced, and since then the output from the mine has steadily increased up to about 1000 tons per annum. No zinc ore is produced at Leadhills.

The veins[edit]

Practically all the Scottish lead veins are of the type generally known as cavity fillings or fissure lodes." Simple veins with well-defined walls are the most common, and they often show evidence of repeated opening and refilling of the fissures. In the Newton Stewart area, on the other hand, many of the veins are of a composite nature; their walls are ill-defined, and the country-rock is much broken up and strung through with veinlets of ore. The " bearing-ground," as this impregnated zone is called, may be as much as 20 yds. in width, and is liable to contain pockets of ore at any part of its course, after the manner of a stockwork.

In a general way the contents of the veins may be divided as follows:

a. The Ores, Main and Accessory (1) Primary ores as originally deposited. (2) Secondary ores (due to alterations, of the primary ores).

b. The Gangue Minerals.

c. Rock Inclusions.

The distinction between main and accessory ores' is, of necessity, governed by the economic conditions prevailing at the time, and by improvements of plant or in method of working an accessory ore may become of sufficient value to repay the cost of extraction, and may even become the principal ore for which the deposit is worked. In many of the Scottish veins the ore is complex, being an intimate mixture of various minerals which are too finely disseminated to be separated from one another, or from the gangue, by ordinary washing processes. In former times the miners were unable to cope with this type of ore, and it was often left in the mines or thrown away on the dumps. With the improved machinery and processes now available these mixed ores can be worked up, and the different minerals separated. At the present time plant is being fitted up to deal with some of the old dumps containing these complex ores.

The following tables give the common ores of lead and zinc as found in Scotland, the percentage of metal being the theoretical amount present in the minerals:

Lead ores

Ores

Chemical Composition. Percentage of Lead.
Primary Galena PbS 86.6
Primary Jamesonite Pb,Sb2S5 50.8
Secondary Cerussite PbCO3 73.0
Secondary Anglesite PbSO4 68.3
Secondary Pyromorphite Pb5Cl(PO4)3 75.8
Secondary Mimetite Pb5Cl(AsO4)3 69.6

At the present time galena is the only ore worked, but a little jamesonite is occasionally met with. In the early days cerussite and pyromorphite were worked in the oxidised portions of some of the Leadhills veins.

Zinc ores

Ores. Chemical Composition. Percentage of Zinc.
Primary Sphalerite, Blende, or "Black Jack ZnS—(Fe and Mn). 50-67
Secondary Calamine. ZnCO3. 52'0
Secondary Hemimorphite. H2Zn2SiO5 54'2

Sphalerite is the only zinc ore mined in Scotland.

The metallic sulphide ores usually contain small quantities of the precious metals, but up to the present silver is the only one extracted from Scottish lead and zinc ores. The amount of silver varies greatly in ore from different localities, and even in ore from any one mine. The galena formerly raised at Coire Buidhe Hill, on the south side of Loch Tay, is said to have yielded 600 oz. to the long ton, but this is exceptional, and the amount of silver in Scottish lead usually runs from 2-10 oz. to the long ton. The amount of gold present in the ore is minute and often has not been estimated. In a complex lead-zinc-copper ore formerly worked at Stronchullin,[26] near Ardrishaig, the gold present reached the exceptionally high value of 4 oz. to the ton, and for a short time this mine was reopened and worked for gold; but the rich pocket soon became exhausted, and the work was abandoned. An assay of the complex ore now being worked at Wood of Cree gave 2 dwts. of gold to the long ton.

Gangue Minerals

The common gangue minerals of the veins are quartz, calcite, dolomite and barytes. In many instances they occur in subordinate quantities only, and usually are too much mixed with impurities to be of economic value. In fact, in some cases they are detrimental. For instance, the presence of barytes in conjunction with zinc-blende makes the separation of the latter in a pure state a, rather difficult task owing to the two minerals having similar specific gravities.

Rock Inclusions

Much of the material in the veins consists essentially of a breccia of country-rock cemented together by ore-bearing gangue minerals. Consequently a large quantity of rock has to be worked and brought to the surface, and after the extraction of the ore the residue may be divided into three main categories:—

  1. Hand-picked tailings
  2. Gravel and sand
  3. Slimes

The first are of little value except for road-metal or railway-ballast, but the other two are now finding a use in the manufacture of concrete and cement, and at the present time are worth as much as 10s. per ton.

Distribution of the veins[edit]

In the following account of the occurrences of mines and veins of lead and zinc ores in Scotland, it has been found convenient to divide the country into a number of areas, arranged more or less geographically from south to north. These are as follows:* The Southern (Area I.)

  • The Central (Area II)
  • The Northern (Area III.)
  • The Orkneys and Shetlands (Area IV.)

(Plate 1) is a map of Scotland showing the localities of the mines and veins, and the boundaries of the individual areas. In the preparation of this map the opportunity has been taken of producing a general index map showing the localities of the majority of our mineral veins, and with this object it is not limited to those of lead and zinc, but occurrences of ores of copper, nickel, antimony, etc., are also shown, in the hope that it will be of use to people interested in the subject. By the use of this map, in conjunction with the general list of veins given in the index at the end of this volume, the position of any particular locality can easily be found. Many of the veins are sporadically distributed over the country, but more often they occur in groups, which are usually restricted to certain types of country-rock. In some cases the veins of one group may all belong to a single system and have a common trend. In other cases there may be two or three systems of veins with different trends, and cutting one another at various angles.


In a general way the Scottish veins can be divided into four main systems according to direction, namely, north-east, east-and-west, north-west, and north-north-west.

References[edit]

  1. J. R. S. Hunter, The Silurian Districts of Leadhills and Wanlockhead, Trans. Geol. Soc. Glasgow, vol. vii., 1884, p. 376.
  2. Daniel Wilson, Prehistoric Annals of Scotland," vol. ii., 1863, p. 64.
  3. Pennant, A Tour of Scotland, vol. ii., 1790, p. 250.
  4. G. V. Irving, The Upper Ward of Lanarkshire, 1864, vol. i., p 50
  5. Cochran Patrick, Early Records Relating to Mining in Scotland, 1873, p.xxxiv.; also Compot. Camer. Scot. (Bannatyne Club), vol. i., p. 48.
  6. Cochran Patrick, Early Records Relating to Mining in Scotland, 1873, , p. xxxiv.; also Stevenson, Historical Documents, Scotland, vol. i., p. 329.
  7. The (Old) Statistical Account of Scotland, vol. viii., 1793, p. 351.Cochran Patrick, Early Records Relating to Mining in Scotland, 1873, pp. lx. and 2. Scots Acts, vol. ii., p. 5, c. 13.
  8. Cochran Patrick, Early Records Relating to Mining in Scotland, 1873, p. lv.
  9. Cochran Patrick, Early Records Relating to Mining in Scotland, 1873, p. lv.; also Analecta Scotica, p. 20.
  10. Cochran Patrick, Early Records Relating to Mining in Scotland, 1873, p. lv.; also Analecta Scotica, p. 85.
  11. Cochran Patrick, Early Records Relating to Mining in Scotland, 1873, p. lv.; also Analecta Scotica, pp. 91-94.
  12. Lesley, De origins, etc., Scotorum, 1675, p. 11.
  13. Cottonian MS. (Reprinted by J. R. S. Hunter), The Silurian Districts of Leadhills and Wanlockhead, Trans. Geol. Soc. Glasgow, vol. vii., 1884, p. 388.
  14. Cochran Patrick, Early Records Relating to Mining in Scotland, 1873, p. a-v.; also Compota Thesaurarii, 1539-40. MSS, Reg. Ho., Edin.
  15. Cochran Patrick, Early Records Relating to Mining in Scotland, 1873, pp. xviii., 98.
  16. Cochran Patrick, Early Records Relating to Mining in Scotland, 1873, pp. iv., 101; also Scots Acts, vol. iv., p. 84, c. 71.
  17. Atkinson, Discovery and Historie of the Gold Mynes in Scotland (Bannatyne Club, 1835), p. 47; also Cochran Patrick, Cochran Patrick, Early Records Relating to Mining in Scotland, 1873, p. xxxvii.
  18. Cochran Patrick, Cochran Patrick, Early Records Relating to Mining in Scotland, 1873, p. xliii.
  19. Williams, The Natural History of the Mineral Kingdom, vol. ii., 1810, p. 479.
  20. The (Old) Statistical Account of Scotland, vol. vii., 1793, p. 54.
  21. The (Old) Statistical Account of Scotland, vol. iv., 1792, p. 263.
  22. Cochran Patrick, Early Records Relating to Mining in Scotland, 1873, p. xxxiv, and Acta Dominorium Auditorum, p. 6.
  23. Balcarras MS., Anelecta Scotica, First Series, pp. 91-94
  24. Hume Brown, Scotland in the Time of Queen Mary, 1904, p. 228.
  25. The Geology of Knapdale, Jura, etc." (Mem. Geol. Surv.), 1911, p. 135