Brandy Gill exposes a remarkable variety of altered gabbro. Near the southern margin of the complex, biotite replaces the primary mafic minerals extensively, while sericitization and albitization of plagioclase feldspar have occurred. Moving away from the contact, actinolite is common as a replacement of the primary amphiboles and pyroxenes, chloritization of the feldspars is nearly complete, and ilmenite is altered to titanite.

Around 500 meters upstream from the Carrock mine, an east-west lead vein crosses Brandy Gill and has been explored from levels on both banks of the gill. While the levels on the west bank have been investigated in recent times and shown to be mostly barren, the lower level exhibits some stoping activity. This mine, assumed to be the one referenced below, has records of lead and copper mining dating back to the early 18th century. However, there are no known records of mining activities before 1852. The mine operated sporadically until around 1873, with only a few tons of lead and copper ore being raised.

In 1875, J.G. Goodchild of the Scottish Geological Survey discovered wulfenite in Brandy Gill, but it wasn’t until the 1950s that the locality gained interest among collectors. This interest was sparked by the report of a suite of rare supergene minerals, including bayldonite, duftite, beudantite, carminite, lindgrenite, etc. Stolzite, the first authenticated British occurrence, was also found here.

1863-1872 Leicester M. Hutchinson & Co. 1875-1877 M. Hutchinson & Co.