The type description (Cabri et al, 1970) indicates that nisbite is very rare at the locality and that it easily mistaken for fine grained gudmunite. The two minerals can only be distinguished by analyzing individual grains. Cabri et al. (1970) found nisbite as irregular grains up to 20 micron in size.
Trout Bay Copper Mine, Mulcahy Township, Kenora District, Ontario, Canada