Abstract: Gyrolite containing no detectable Al (<0.04 wt.%) has been found as aggregates of platey crystals to 6 mm at Dean Quarry, the Lizard, Cornwall. The gyrolite occurs embedded in calcite which fills a fracture vein in gabbro. Paragenetic evidence is inconclusive, but suggests that gyrolite formed relatively early, after prehnite, and possibly around the same time as analcime and natrolite.