‘Hartite’ renamed branchite

Historical samples of branchite, described by the Tuscan naturalist Paolo Savi (1798–1871) at the end of the 1830s, were re-examined through single-crystal X-ray diffraction, showing their identity with hartite, C20H34, a hydrocarbon mineral described by Haidinger in 1841. The refined unit-cell parameters are a = 11.4116(7), b = 20.9688(12), c = 7.4100(4) Å, α = 93.947(2), β = 100.734(2), γ = 80.524(2)°, V = 1716.99(17) Å3 and Z = 4; space group P1. The crystal structure was solved and refined up to R1 = 0.0424 for 13512 reflections with Fo > 4σ(Fo) and 1265 refined parameters. As the name ‘branchite’ has priority over ‘hartite’, the reinstatement of the former name and the discreditation of the latter were approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA–CNMNC). Branchite is one of only eleven minerals formed by C and H listed in the official IMA List of Minerals. The type locality of branchite is the Botro di Lavajano, Monte Vaso, Chianni, Pisa, Tuscany, Italy. Neotype material is kept in the Natural History Museum of the Pisa University under catalogue number 14426.