Reference materials for iron speciation analyses. Four reference materials are available (see Alcott et al., Geostandards and Geoanalytical Research, v44, 581-591, 2020): WHIT; KL133; KL134; BHW. Cost is £200 for 50 g of one reference material. Price includes postage and packaging, and UK taxes. Maximum purchase of 50 g of each reference material. Samples should be stored in a desiccator or freezer upon delivery to minimize long-term oxidation of reduced Fe minerals.