MINERALOGICAL NOTES

from the Leadhills--Wanlockhead mining district, Scotland THE Leadhills-Wanlockhead orefield is a well known locality for fine mineral specimens (Gillanders, 1981); to date more than 70 species have been recorded including the only known occurrence of a natural sulphite, scot-landite (Paar et al., 1984). However, magnetite, pyrrhotine and pentlandite, have not previously been recorded from this area. Magnetite occurs in reddish-brown blocks on the mine dumps near Whyte's Cleugh [NS 870 138]. These blocks also contain abundant rugs which are lined with euhedral quartz crystals. The mineral was identified initially by its optical characteristics n reflected plane polarised light, which are similar to those given in Uytenbogaardt and Burke (1971). Subsequently, the blocks were crushed and the magnetic material separated prior to analysis by X-ray powder diffraction. This confirmed that the mineral was magnetite and not maghemite which has similar optical properties. Lamellae of hematite were commonly observed within the magnetite. Pyrrhotine occurs as small grains up to 250 #m long in samples of greywacke collected from the Glencrief Burn, adjacent o several small quartz veins [NS 867 128]. Marcasite, pyrite, chalcopyrite, sphalerite and galena re disseminated through the greywacke, being particularly concentrated near these veins. Identification by reflected light microscopy was confirmed by semi-quantitative electron microprobe-EDS analyses. These gave a range of compositions: Fe 61.1-58.5 wt. %, 48.0-45.1 at. %; S 38.1-41.0 wt. %, 52.0-55.0 at. %. A comparison with the theoretical pyrrhotine composi-tion range of FeS to Fe7S 6 gives Fe 63.5-60.4 wt. %, 50.0-46.7 at. %; S 36.5 39.6 wt. %, 50.0-53.3 at. %; and to that of smythite Fe3S 4, Fe 56.7 wt. %, 42.9 at. %; S 43.3 wt. %, 57.1 at. %. This demonstrates that the Leadhills examples vary in TABLE 1: Mean electron microprobe (EDS) analyses