Abstract: The result of electron probe microanalyses, along with X-ray and optical data obtained for tin sulphides from two different localities in south-west England indicate that the mineral hitherto described from St Michael’s Mount as stannite is in fact kesterite, Cu₂(Fe_0.23Zn_0.77)SnS₄. The yellow ‘stannite’ reported from this locality proved to be stannoidite, Cu₈(Fe_2.39 Zn_0.61)SnS₂S₁₂. Kesterite, Cu₂(Fe_0.09Zn_0.90SnS₄, and zincian stannite, Cu₂(Fe_0.63Zn_0.38)SnS₄, are also reported from Cligga Head. It is suggested that a more cautious approach should be taken in identifying these tin sulphides solely on their optical properties.