Abstract
Extensive substitution of Ni for Zn in hydrozincite from the Parc Mine, North Wales, has been observed. This is the first time that a substantial concentration of another transition metal in this mineral has been reported. The average composition of the nickeloan hydrozincite is Zn (sub 4.63) Ni (sub 0.37) (CO (sub 3) ) (sub 2) (OH) (sub 6) . The relationship of this new variety to other secondary carbonate-containing nickel minerals is discussed, as is the possibility of substitution of other transition metal ions into the hydrozincite lattice.