Chemical composition of 18 ion adsorption deposits (lateritic soils) from Ambohimirahavavy alkaline province, North West Madagascar as part of NERC funded SoS RARE in 2016. Samples collected from pits at depths down to 6.5m below surface. Details of samples in dataset “Sample list for the SoS RARE project” (https://webapps.bgs.ac.uk/services/ngdc/accessions/index.html#item165705 ). Chemical composition of biological and chemical leachates from one Madagascan sample. Time series covers 60 days leaching during 2016 and results are in mg/kg of original material. Biological leaching agents: Aspergillus sp. And Bacillus sp. Inoculum and natural community and chemical leaching agent: ammonium sulphate. Details of experimental procedure in https://doi.org/10.3390/min8060236. Experiments conducted at the British Geological Survey to assess suitability of bioleaching as a more sustainable alternative to chemical leaching of rare earth elements from ion adsorption deposits.