Andreybulakhite, ideally Ni(C2O4) · 2H2O, is a new member of the humboldtine group, named in honour of Andrey Glebovich Bulakh of Saint Petersburg State University. The mineral was discovered at the Nyud-II (Nud-II) Cu–Ni sulfide deposit, Monchegorsk mafic–ultramafic pluton, Kola Peninsula, Russia. Andreybulakhite forms segregations of platy to prismatic crystals up to 2×1×1 µm in size that are localized in the upper part of the fruiting bodies (apothecia) of Lecanora cf. polytropa lichen, whose colonies overgrow the oxidized surfaces of pyrrhotite–pentlandite–chalcopyrite ore. The mineral is monoclinic, with space group C2/c, a = 11.8392(5) Å, b = 5.3312(2) Å, c = 9.8357(7) Å, β = 126.723(5)°, V = 497.59(3) Å3 and Z = 4. The Raman spectrum of andreybulakhite contains the following bands (cm−1): 1701 (C=O stretching vibrations and/or multiphonon processes); 1621 (H2O bending vibrations); 1454 and 924 (C–O and C–C stretching modes); 597 (Ni–O stretching, C–C–O and O–C–O bending vibrations); and 550, 307 and 226 (predominantly Ni–O stretching and deformation modes). The absorption bands of the infrared spectrum are (cm−1) 3389 (O–H stretching vibrations), 1640 (H2O bending vibrations), 1357 and 1315 (C–O stretching, C–C stretching), and 818 (Ni–O stretching, C–O and C–C stretching, C–C–O and O–C–O bending vibrations). The empirical formula calculated on the basis of (Ni + Cu + Mg + Co) = 1 atom per formula unit is (Ni0.63Cu0.27Mg0.08Co0.02)61.00(C2O4) · 2H2O. The absence of iron in the mineral is a result of oxidative Ni2+/Fe3+ fractionation during the secondary aqueous alteration of Ni- and Cu-rich sulfides. Andreybulakhite has synthetic Ni and Co counterparts; the latter implies the possibility of formation of its Co analogue in a related cobalt-rich environment.