A diopside-bearing pegmatite near Ellon in Aberdeenshire

I ntroduction . A t Michaelmuir, 3½ miles north-west of Ellon in the Buchan district of Aberdeenshire, a narrow belt of metamorphic rocks of sedimentary origin separates the two great igneous and contaminated masses of Haddo and Arnage. This belt is made up of the Fyvie Series 1 of the Highland Schists of Northeast Scotland, a series predominantly composed of andalusite-cordierite-schists and pebbly grits. At a few localities in Buchan, such as Michaelmuir, Auchnagatt, and Ardlethen, thin limestones occur within the Fyvie Series. East of Michaelmuir, where the sedimentary belt separating the Haddo and Arnage igneous masses crosses the Ythan, abandoned quarries are situated on these limestone outcrops. Quarries are found at Quarrybrae of Auchedly on the west bank of the river, and between Waulkmill Hill and Shallowplough on the east bank. In all these limestone quarries there are pegmatite veins of some interest. Thus, at Quarrybrae of Auchedly, excellent graphic pegmatites and tourmaline-biotite-pegmatites are to be seen. East of the River Ythan, over the ground leading from Shallowplough westwards to the main Ellon-Methlick road, biotite-pegmatites, often beautifully graphic, are well developed, whilst in the eastern limestone quarry at this locality there are several veins which furnish the subjects of this communication. T he D iopside -P egmatites . In the eastermost quarry, ⅜ mile west-south-west of Shallowplough, the vertical limestone is traversed by several veins well exposed on the eastern wall of the quarry. The first vein to be considered occurs towards the northern end of the eastern wall. It