On the Occurrence of Chloritoid in Kincardineshire

Abstract

In the neighbourhood of Drumtochty, near Fordun, I found numerous fragments of a green schist, which are characterized by white or yellowish spots. On closer examination these specimens disclose numerous minute, dark, glistening crystals, which are fairly evenly distributed. Several of these were picked out with the point of a knife, when they proved to be hard and brittle. Placed on a sheet of white paper, the crystals were seen to be rudely hexagonal and dark green by transmitted light. Their characters and mode of occurrence suggested that they were chloritoid, or ‘brittle-mica’ and subsequent investigation has proved that this is their true nature. The rock containing them was first met with in situ , at the entrtmce to the little gully at the head of Friar Glen Burn, near Drumtochty Castle. The section here shows a highly chloritic green grauwacke, becoming gradually finer in texture, and passing into the spotted green schist containing the chloritoid, which may be conveniently called the ‘chloritoid-rock.’ A few inches of grey, almost metallic-looking schist succeeds this, and farther on is a rather yellow schist, with small crystals of brown mica. This passes gradually into a schistose pebbly grit of the arkose type: that is, the pebbles are embedded in what was originally a fine arkose matrix, as distinguished from the chloritic matrix of the green grauwacke. This sequence of rocks is easily recognized, and we have now succeeded in finding it in a number of localities along a narrow belt of ground nearly 22