Heavy mineral sands are common on the beaches of the Belmullet Peninsula and Achill Island as well as southern outer Clew Bay. The combination of metamorphic and igneous terrain adjacent to high energy coastlines offers a clear scenario for heavy mineral sand development in Ireland. This survey took place in July-August 2017 on board the Marine Institute's R.V. Celtic Explorer, led by University College Cork (UCC). This survey focused exclusively on studying offshore heavy mineral sand deposits in the Blacksod/Achill Island/SW Clew Bay area and provided data to the SFI-funded iCRAG (Irish Centre for Research in Applied Geosciences) project FLIPeR (Formation of Littoral and Offshore Irish Placer Resources). A series of areas were surveyed to locate, delineate and sample heavy mineral sands near to beaches where heavy minerals had already been sampled. All areas surveyed were mapped with non-overlapping multibeam lines at 250m or 500m apart. Magnetometer data and seismic and sub-bottom profiler data was collected, and CTDs (Conductivity-Temperature-Depth) were taken to calibrate the sound velocity for the multibeam echosounder. To map the spatial and volumetric extent offshore heavy mineral sand deposits To retrieve samples to quantify the amount and type of heavy mineral sands and enable heavy mineral sand grain analysis for provenance studies and assays. To retrieve cores through heavy mineral sand deposits to look a variation in heavy minerals sands through time and relate to temporal changes in environmental conditions and to allow better quantification.