Amorphous calcium carbonate (ACC) is a transient phase in one of the most important biomineralisation systems in animals (s.g.) such as crustaceans. The literature reports many structural techniques applied to ACC, but neutron diffraction of ACC has not be reported. This proposal is to use SANDALS to measure the structure factor of ACC for the first time. The results will be analysed by peak fitting and comparing with models using EPSR. The proposal previously received beamtime but deuteration of the sample proved problematic. We are now confident about a second attempt at deuteration (see updated details in experiment description). This seems a worthwhile goal given the scientific importance of ACC.