An historical and geological assessment of a Scottish building stone quarry : Drumhead Quarry, Denny

Drumhead Quarry, situated a few kilometres north-east of Denny in the Central Belt of Scotland, is one of several quarries in the Falkirk area which exploited the Cowie Rock, a pale-coloured sandstone in the Upper Limestone Formation (Clackmannan Group). The quarry supplied building stone from the very early 18th century, working fairly consistently until the late 19th century. Historical evidence indicates that the stone was primarily used locally in the Falkirk and Stirling areas, until the opening of the Union Canal in 1822 which then allowed the sandstone to be shipped to Glasgow, Linlithgow and Edinburgh, mainly for use as paving stone. Drumhead sandstone was the first ever shipment along the Union Canal in 1822, landing in Edinburgh. The quarry was worked under several different operators throughout the 19th century and often shared the same operator as Thorneydyke Quarry (located c. 600m to the north) in the latter half of the 1800s. It was not uncommon for the quarry to be operated by local builders and architects, who were most likely to use the stone they were extracting from their own quarry as the main source of building material for their designed and built structures. Drumhead Quarry exposes thick-bedded sandstone with some bedding lamination and wide joint spacing, well-suited to extracting large blocks. The possibility that a unit of limestone - the Calmy Limestone - encroaches near to the quarry‘s east and north boundaries (and might limit the prospects for future expansion) has been recently tested by drilling boreholes. Limestone was not encountered in the drilling exercise, but units of mudstone and shale interbedded with sandstone to the east of the quarry indicate a change in the depositional environment of the sedimentary rocks in this area, and suggest the limestone might be nearby. A borehole to the north of the quarry encountered only sandstone in the bedrock, hence extending the quarry in this direction would appear to offer the best prospect of encountering good reserves of sandstone. Samples of Drumhead sandstone are quartz-rich, well compacted, and have a strong natural mineral cement resulting in a strongly cohesive (difficult to disaggregate) stone. The stone is therefore of good quality and likely to be durable. It has the potential to be a versatile building stone, suited to a range of uses including rubble walling, high quality ashlar and carving. There are two main varieties of the sandstone: a buff variety with faint-to-strong bedding lamination, and an off-white, freestone (uniform) variety. All of these factors will enhance the commercial viability of the stone. The two varieties of Drumhead stone should provide a good substitute for a number of sandstones that were formerly sourced and used widely in the Central Belt, but are now unavailable. Sandstone of this type is in particular demand in the Stirling, Glasgow and Linlithgow areas.