Dunkeld slate quarries, Highland Border 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.

Dunkeld[edit]

Sketch map of the slate quarries near Dunkeld. P519826.
Map of Highland Border slate belt. P519823.

Maps[edit]

Sheet 47 Crieff. 1:63, 360 geological map.

Six inches to the mile: Perth, Sheet 62 S.W.

General description[edit]

The Aberfoyle Slates outcrop on both sides of the Tay Valley ½ ml. to 1 ml. S.E. of Dunkeld railway station. As shown on the geological one-inch map (Sheet 47) the breadth of outcrop is less than a quarter of a mile, but a recent geological revision suggests that the outcrop is much broader – about half a mile. The quarries, which have been abandoned for at least 40 years, include the Birnam Quarries, on the W. side of the river, and the Newtyle Quarries, on the E. side; these are described separately below.

Birnam quarries[edit]

Locality On a steep hillface W. of the main road and railway, 1 ml. S.E. of Dunkeld railway station.
Access The workings are close to road and rail but extend to a height of 450 ft. above the railway; the higher openings are difficult of access, being reached only by a rough zig-zag track.
Description of slate Colours grey, purple and green with good proportion of last-named; banding moderately common, showing most clearly in green varieties; surface even, somewhat rough; texture fine to medium, pyrites crystals (‘diamonds’) very sparse and small.
Dips, with amounts Cleavage-dip W. 25º-35º N. at 45º to 60º. Bedding-dip often coincides with cleavage-dip but locally differs (producing banding) owing to presence of small-scale folds.
Joints The slates are considerably broken up by joints in places, but it is difficult to generalise regarding their direction.

Details of workings[edit]

The slates have been worked in a series of openings extending south-south-westwards up a steep hillside. The three lower quarries are probably in the same seam, which is limited to W. by a band of valueless, slightly gritty rock. The uppermost quarries may be in another seam passing slightly to the east of that worked at lower levels, or may be in the same seam shifted slightly E. by a fold or fault.

The lowest opening is adjacent to the railway and has been worked as a sinking below general ground level. It is now partially filled with debris and town refuse. Two large openings occur 300 yds. southwards and farther up the hillside. These must have been worked in a band of slate-rock 40 to 50 ft. wide and may each have been up to 100 ft. in height, but they are now so badly obscured by debris that no detailed examination is possible. Not far above the uppermost of these two large openings there are two smaller levels close to each others, each in about 30 ft. of slate-rock, mainly of a greyish-green colour. On the west wall of the more northerly opening, small-scale folding of the bedding is well seen, with the cleavage maintaining a constant dip at 60º in a direction 30º N. of W. It thus crosses the bedding at various angles. The axial planes of the folds are parallel to the cleavage, with the easterly limb of an anticline dipping at a steeper angle (almost parallel to the cleavage) than the westerly limb. A sixth, and top, level occurs above those just described. Although this level is somewhat obscured by debris, it is apparent that about 50 ft. of slate-rock has been worked. This includes a band about 12 ft. wide at the extreme S.W. edge of the quarry which appears to contain particularly good purple and greenish slate. To N.W. of the 50 ft. band there is a quartz-vein and probably a vertical fault striking N.E. Beyond this break more slate-rock has been quarried, but it seems to be of poor quality. Overburden is light.

Reserves[edit]

It would be very difficult to reopen the lower levels owing to debris. The higher workings are not so seriously blocked and could be extended to the south-south-west, but access would be difficult.

It might also be possible to locate an entirely new band of workable slate in the crags to N. of the old workings.

Newtyle quarries[edit]

Locality On hillside E. of road and R. Tay, 1 ml. E. by S. of Dunkeld railway station.
Access The workings lie about 200 yds. back from, and 150 to 200 ft. above, the road on E. side of R. Tay.
Description of slate Colours grey, purple and green with good proportion of last-named; banding moderately common, showing most clearly in green varieties; surface even, somewhat rough; texture fine to medium, pyrites crystals (‘diamonds’) very sparse and small.
Dips, with amounts Cleavage-dip N.W. at 50º to 60º. Bedding-dip often coincides with cleavage-dip but locally differs (producing banding) owing to presence of small-scale folds.
Joints The slates are considerably broken up by joints in places, but it is difficult to generalise regarding their direction.

Details of workings[edit]

The slates have been worked in several openings extending across, not along, the cleavage strike and are clearly in different seams. The most northerly opening lies 200 yds. E. by S. of Newtyle Cottage. The face is about 60 ft. across and 40 ft. high. A particularly good band, consisting of 10 to 12 ft. of grey, sometimes greenish, slate occurs at the N.E. corner of the quarry. It has been worked inwards until there is an overhanging roof and also downwards. Another opening has been made about 80 yds. to S.E. The face is about 75 ft. across and 50 ft. high. Purplish slates are plentiful and near the north-west side green seams occur mixed with inferior rock. A short distance further to the south-east there is a larger opening fully 100 ft. across. It is partly filled with debris and town refuse, while the lower portion of the face is obscured by slipped material. A higher bench of comparatively small size has been developed above the S.E. face (P519826) . It is possible this might be extended as a gallery round the quarry.

To S.E. of the three openings just described there is a belt consisting largely of grit containing subordinate thin bands of slate which have been opened up in several trial cuts. A wider band of slate occurs still further to S.E. and has been worked in a quarry about 50 ft. across and at least 50 ft. high; it is now largely choked with debris.

Reserves[edit]

It would appear possible to extend the three most northerly openings near Newtyle Cottage to N.E. or else to make new levels slightly higher up the hillside on the line of strike of the same seams as those exposed in these old workings. The overburden is slight, but the top-rock is broken. As development is thus possible at a much lower level, relatively to a road, than is the case with the Birnam Quarries, the Newtyle Quarries would appear to afford a more favourable subject for further exploitation.