Data characterising the composition of mine by-product materials. Samples were taken from 2 mines; a Platinum mine north of Mokopane, Limpopo Province, South Africa and Smelter operations near Polokwane, Limpopo Province, South Africa. Data consists of: Particle size analysis (by dry sieving or laser analysis, as appropriate) X-ray diffraction determination of mineralogy of mine tailings materials. Whole rock geochemistry determined by XRF, with total carbon, total organic carbon, total inorganic carbon and total sulfur determined using a LECO elemental analyser. Samples were collected in the field 18-22 February 2019, sample size characterisation and XRD analysis were carried out in May 2019 and geochemical analyses were conducted June-August 2019. Data were collected as part of NERC grant NE/P019536/1:Releasing divalent cations to sequester carbon on land and sea Published in: L.A. Bullock, A. Cunningham, J. Matter, D. Hasson, E. Smith, M.T. Duret, E. M. Mervine, R.H. James and D.A.H. Teagle (2026) Dissolution kinetics of platinum mine by-products for nature-based ad engineered carbon dioxide removal. Applied Geochemistry 207, 106964 Doi: 10.1016/j.apgeochem.2026.106964