In the late C18th the Duke of Hamilton’s factor on the island, John Burrel, initiated a series of schemes to reorganise land tenure on the island and provide a diversify employment opportunities with the purpose of making the Duke’s Arran estate more profitable. In the decade from 1772 he amalgamated the runrig system of agricultural holdings into small farms and started a number of extractive industries.
On Creag Ghlas Cuithe between Lochranza and Laggan a band of slate is exposed in the core of a large recumbent anticline (the Tay Nappe) and this represents the top of the Dalradian Southern Highland Group of schists and slates on the island. There are records in the Earl of Arran’s estate accounts, kept at Brodick Castle, recording that between 200,000 & 300,000 roofing slates were sold each year between 1776 and 1781. Although it is reputed that the Lochranza slate was inferior to the slate produced further north in Argyle from the slate debris around the former workings it is clear that the slate spit cleanly and that there are no pyrite crystals in it, unlike the Ballachulish slate. It is still possible to see the smaller Lochranza slate on many of the older buildings around the island. The exact date that the slate quarry closed is not known due to incomplete records, but it is probably within a few years of the final records in Brodick castle.
The cache is most easily approached from the old post track from Lochranza to the abandoned village of Laggan; once the track flattens out above Glen Chalmadale the remains of the old track up to the quarry workings can be seen on the hillside to the south. It is also possible to approach from the summit of the Boguillie road over Creag Ghlas Laggan, although this will involve a 5 km journey over trackless peat bog and mountain side.
The old workings are quite subdued and the main workings provide a sheltered picnic spot on a windy day. A couple of hundred metres southwest of the main workings there are two small water filled test pits but the main danger in this area is falling into a peat bog.
