Monument record 9648 - Cnoc Dubh, Gearraidh na h-Aibhne

A vein of tool-quality quartz outcrops on a vertical face behind a modern sheep fank. Negative scars, and semi-circular areas of pecking on the lower part of the vein indicate that small pieces of quartz (c. 20-30cm dia.) have been quarried here. It may be assumed to be prehistoric.
MML 15.1.2002

NB22NW 28 2318 2998

NB 2318 2998 An examination was carried out in September 2002 of a small quartz vein at the knoll of Cnoc Dubh, a few hundred metres from the end of Loch Ceann Thulabhig. The knoll is roughly D-shaped, with an approximately rectilinear rockface running parallel to, and facing the road between Gearraidh na h-Aibhne and Tuimsgearraidh (B8011) to the NW, whereas the curved and gently sloping lee of the knoll faces the boggy interior of the island. The quartz vein covers part of the rockface, with full views of the sea loch and, at a few kilometres distance, the Calanais ritual complex.
The Cnoc Dubh quartz vein consists entirely of homogeneous white milky quartz. The vein measures approximately 12m from NE to SW. Its height varies between c 30-50cm at the NE and SW ends and c 3m at its widest point. The vein has mainly been worked in the most extensive central part, and in the area between the centre and the SW terminal, resulting in prominent overhanging steps of gneiss. Measured from the outermost part of the overhang to the innermost part of the worked vein (c 4.5m from the SW terminal), an estimate of c 1m of quartz has been removed. As the worked part of the vein has a length of approximately 4-5m, it is reasonable to assume that c 3m3 of quartz may have been quarried.
A number of attributes define the vein as worked. Most of these are similar to attributes associated with the knapping of lithic cores, such as circular impact scars and denticulated edges. Most prominent, however, is the vein's stepped appearance, which is the result of the gradual removal of natural layers of quartz by prehistoric people.
Sponsor:
Catherine Mackichan Bursary Trust.
T Bjarke Ballin
REPORT DATE: 24/02/2005