OS maps indicate that the quarry had fallen into disuse by the mid-1960s. The path shown in this photograph follows the original course of Barnhill Road. That former road is now no more than a track, but it is still in use as part of a local route, Overtoun House Circular Path. The present-day Barnhill Road follows a rather different course: NS4175 : Barnhill Road, Dumbarton
The former quarry is about 400 metres long (E-W), by about 20 metres wide (N-S), and is in two halves, one higher than the other; the halves are separated by the section of path shown here. To the left of the path, there is a sheer drop (behind a fence) to the lower western part, the older half of the quarry (intervening trees make it hard to show that area photographically). To the right of the path, as shown in the present photograph, is the entrance to the higher and more recent eastern half of the quarry; this part was largely excavated after 1938.
For a view from the opposite end of this half of the quarry, see NS4175 : High Mains Quarry
The back part of the quarry (as it appears in the present picture) has a raised edge, as shown in views from the woods there: NS4175 : The edge of High Mains Quarry
/ NS4175 : The edge of High Mains Quarry
There was a quarry at High Mains at the time of the first-edition OS map (c.1860), but it was then much smaller, and did not extend very far from the vicinity of NS4175 : Strowan's Well
(High Mains Quarry began there, and, over the years, was gradually extended further to the east).