We report low-temperature magnetic properties of predominantly mafic rocks from the Mesoproterozoic Ropruchey sill, Karelia. Based on microscopic observations, the studied rocks can be classified into two groups, granodiorites and gabbro-diorites, with different magnetic mineralogy. In granodiorites, the only magnetic mineral is stoichiometric magnetite characterized by a Verwey transition temperature of 120–121 K. In gabbro-diorites, the magnetic mineralogy is also dominated by magnetite, which however contains 2–3% of Ti substitution atoms, lowering the Verwey transition temperature to 94–103 K. In addition, the gabbro-diorites appear to contain some amount of a more Ti-rich titanomagnetite, as well as another, yet unidentified magnetic phase, manifesting itself by a peculiar temperature and frequency-dependent behavior of magnetic susceptibility.