Spodumene pegmatites were prospected in the early 1970s along the flank of the Leinster granite. Moylisha was one of the larger prospects. There are no outcrops, the pegmatites are known from boulders and drill core.

The simple and spodumene pegmatites at Moylisha form a late Silurian to early Devonian NE-SW-striking pegmatite belt that intruded the East Carlow Deformation Zone along the SE margin of the late Caledonian S-type Leinster Batholith. All analyzed pegmatites contain assemblages including K-feldspar, albite, quartz, muscovite ± spodumene (Keyser et al., 2023).

The spodumene forms laths up to about 20 cm long, and is usually white, though occasionally has a pinkish tint. The area is now under a dense forestry plantation. Occasional boulders may be found along the tracks. The access point for these is at Irish grid ref. S 923 673. In the course of the prospecting work an occurrence of exceptional cassiterite crystals was found. These are up to 2 or 3 cm across, euhedral and in quartz matrix. A fine example is in the Hunterian Museum (specimen GLAHM 111414). They were traced to a single vein exposed in a trench at grid ref. S 9270 6629. The trench is still visible at the top of a field, but is partly filled in and grassed over. There are no outcrops, nor any sign of cassiterite there now.

Li-pegmatite sheets at Moylisha Hill, the focus of this study, are classified as albite–spodumene pegmatites and as Group 1 pegmatites. They were emplaced into the marginal granodiorite of the TLU, within the ECDZ, as a series of unzoned to poorly zoned dykes up to ~20 m thick.
Stage I: Primary Assemblage
Stage II: Potassic Alteration
Stage III: Sericitization
Stage IV: Albitization
Stage V: Late Stage

Other Regions, Features and Areas containing this locality

References