Luing main slate quarries, Easdale slate belt, Scotland

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From: Richey, J.E. and Anderson, J.G.C. 1944. Scottish slates. Wartime pamphlet No. 40. London : Geological Survey of Great Britain.

Cullipool Quarries, Island of Luing[edit]

Sketch map of slate quarries at Cullipool, Isle of Luing. P519822.
Map of Easdale slate belt with inset map showing outcrops near Oban. P519820.

(P519822)

Maps[edit]

Sheet 36 Kilmartin. 1:50,000 geological map

Six inches to the mile: Argyl, Sheet 129 N.E.

Locality W. side of Luing, a mile S.S.W. of Cuan Point, adjacent to the coast.
Access Quay 1/3 ml. S. of Cullipool; village 2½ ml. by road to Cuan Ferry: Cuan Ferry by road to Oban, 13½ ml.
Description of slate Colour, bluish-grey, occasionally banded (‘ribboned’); surface, even and slightly rough, with well-marked grain; texture medium; pyrites crystals (‘diamonds’), split with cleavage of the slate.
Dips, with amounts Cleavage-dip, E. 15º-20º S. at 50º-60º. Bedding-dip, E. 5º-10º S. at 10º to 55º.
Joints In addition to various less constant joints, there is a well-developed set of joints running approximately with the dip of the cleavage, striking approximately N. 60º W. and inclined at high angles (about 85º) to the N.; the dip joints are often spaces at intervals of some 6 to 12 ft.

Details of workings[edit]

The village of Cullipool is situated on a broad, flat platform of the 25-ft. raised beach, which is bordered inland by high cliffs of slate-rock. The platform becomes narrower immediately N. of the village and beyond this point it follows the coast northwards. Present working quarries (Nos. 1, 2 and 3, (P519822) ) are situated along the coastal cliff, and two large abandoned quarries (Nos. 4 and 5, (P519822) ), filled with water, have been excavated in the raised-beach platform respectively to N. and S. of the village.

A belt of slate-rock, 60-70 ft. in depth (measures vertically) has been most sought after. It extends from a point near the coast ½ ml. due N. of St. Peter’s Church, Cullipool, S.S.W. along the cliffs through quarries Nos. 1, 2 and 3, and was also worked in quarries Nos. 4 and 5. At the most northerly exposure the base of this slate-belt is seen overlying a poor quality slate. Other smaller belts of slate have also been worked, and in quarry No. 5 the floor was sunk to a depth of about 100 ft. below the level of the 25-ft, raised-beach platform, that is to say, about 75 ft. below mean sea-level.

The 70-ft. slate-belt is shifted laterally along its course, so that the quarries opened in it are arranged slightly en echelon. The reason for the lateral shift is not clear. Mr. McCowan, the quarry owner, suggests that it may be due to lateral shift of the belt along N.W. whin dykes. Or it may possibly have to do with the folding.

In the quarries such bedding-dips as were noted are nearly coincident in direction with the cleavage-dip, though often lower in angle than the cleavage-dip. A sharp turn-over of the bedding to W. is seen near the entrance to quarry No. 2, marking the centre of an anticline. Another anticline, situated farther W., is evident on the coast near high-water mark 160 yds. to S. of quarry No. 2. The details of the geological structure, however, have not been worked out.

Along the cliffs there is little or no overburden of superficial deposits, except at one point near the centre of quarry No. 2, where there is a hollow at the top of the cliff filled with about 12 ft. of sand and gravel overlain by a bed of peat. As in other districts, the slate-rock along the cliffs, were not protected by superficial deposits, is weathered and useless to a depth of 6 ft. or so; on the other hand, along the raised-beach platform, as for example in quarry No. 5, the slate-rock is exploitable practically to the surface, even where the covering of superficial deposits is very thin.

Reserves[edit]

The present working quarries are Nos. 1, 2 and 3 (P519822) . Nos. 1 and 2 are relatively narrow cuts into the coastal cliff, with floors a few feet above high-water mark. A large quantity of slate-rock remains to be exploited. In quarry No. 3, the working face borders a high-level gallery, and there is hereabouts a large amount of slate-debris. There appears to be a considerable thickness of weathered slate at the top of the working face.

Large reserves occur on the raised-beach platform immediately to the S. of quarry No. 5, extending over about 1/3 acre. Below this strip of ground the 70-ft. slate belt should occur. The strip extends southwards between the raised-beach cliff and the road as far as a point where the platform is crossed by a series of whinstone dykes.

Tir-na-Oig Quarry, Island of Luing[edit]

(P519820)

Sheet 36 Kilmartin. 1:50,000 geological map

An isolated quarry in the Cullipool district is situated at Tir-na-Oig, about 1½ ml. S. of the village of Cullipool and adjacent to the coast, where a jetty has been built for the quarry. The quarry was in operation till recently. A road passes Upper Ardlarach, 500 yds. N.E. of the quarry, which is situated in the cliff of the 2-ft, raised beach, here represented by a narrow platform. The quarry was not visited, but the following details have been supplied by the quarry-owner, Mr. J.S. McCowan.

The general dip of the cleavage is much the same as at Cullipool. Slabs of good size separated by clean joints are obtained, measuring up to 10 ft. in length. The height of the quarry-face, measured from the floor level last worked, is 50 to 60 ft., with overburden of earth 8 to 10 ft. thick. Between the present workings and the sea there is a flat piece of ground, approximately 2 acres in area, which could be developed; slate-rock is to be seen beneath the turf.

Toberonochy Quarry, Island of Luing[edit]

(P519820)

Maps[edit]

Sheet 36 Kilmartin. 1:50,000 geological map

Six inches to the mile, Argyll, Sheet 129 S.E.

Locality Working quarry, immediately S. of Toberonochy village, 140 yds. W. of the coast of Shuna Sound, 2 ml. N. of the S. end of the Island of Luing.
Access Quay of Shuna Sound adjacent to quarry, 3 5/8 ml. by road to Cuan Ferry (Cuan Ferry by road to Oban 13½ ml.).
Dips, with amounts Cleavage-dip, E. 20º S. at 40º to 57º. Bedding-dip, E. 3º S. at 45º.
Description of slate Colour, bluish-grey; surface, even and slightly rough (grain well marked); texture fine to medium; practically free from pyrites.

Details of workings[edit]

The quarry (Breadalban Quarry) extends for about 200 yds. along the strike of the cleavage and is some 70 yds, in width, and approximately 175 ft. in depth, with steep sides all round. The slate is raised by means of a crane, worked by 45 h.p. Crossley engine, to the top of the E. face from where a tramway runs to the quay 200 yds, distant. The bottom of the northern part of the quarry is at present filled with water but the floor of the southern part which lies at a higher level, is dry.

Dip-joints inclines to N. at about 85º are well developed. A knob of worthless slate, in part at least limy, projects from the middle of the western face. A whin ‘bar’, a basalt dyke 3 ft. in width, forms the N. end-wall of the quarry. A considerable amount of quartz-veining roughly following the cleavage occurs here and there, especially along the E. face.

Overburden is thin or absent except around the S. end of the quarry where the slate-rock is overlain by about 8 ft. of sand and gravel. The rock at the surface is little affected by weathering.

Reserves[edit]

The quarry might be extended a short way to the north, but the main reserves lie to the south, along the bottom and sides of the quarry and especially along a stretch of ground about 60 yds. or so in length which remain between the S. end of the quarry and the boundary of the present leas-hold. Other apparently attractive reserves lie between the southern half of the eastern (seaward) face and a sharp fall in the ground facing the sea some 50 yds. to the east. The cleavage-dip being towards the sea, this strip of slate-rock could possibly be exploited, if desires, by working up-dip along the sharp fall in the ground in the direction of the existing quarry. A rock-cutting has been driven through this strip from the top of the quarry, and the quality of the slate appears to be satisfactory.