Summary: A physical, chemical, and preliminary structural study of maucherite (Grünling, 1913) from Eisleben, Thuringia, and Sudbury, Ontario, and temiskamite (Walker, 1914) from Elk Lake, Ontario, shows that these materials have identical specific properties and therefore represent a single mineral species. Previous observations on the artificial crystals and on placodine (Breithaupt, 1841) leave no doubt that these substances are identical with the natural mineral. While admitting the possibility that Breithaupt described natural material, and giving credit to Walker for his independent discovery of the species, it is proper, and in keeping with the present usage, to retain the name maucherite for this mineral. The new observations lead to the following characterization of maucherite:

Tetragonal; a:c = 1:3·190 (from X-ray measurements). Forms: c(001), t(103), v(203), l(101), g(504), h(302), k(201), q(301). Habit, tabular (001) to bipyramidal (101); also radial-fibrous and granular. Twinning common, on (106)? Structure cell, a 6·844±0·01, c 21·83± 0·05 Å.; contains Ni₄₄As₃₂ = 16[Ni₃As₂]-4Ni; a well-marked pseudocell has a′ = a/2, c′ = c, and contains Ni₁₁As₈ = 4[Ni₃As₂]-Ni. Cleavage not observed. Talmage hardness, E. Specific gravity, 8·00 (measured on best material), 8·04 (calculated). Fresh surfaces reddish platinum-grey, with bright metallic lustre. Polished sections pinkishgrey, weakly anisotropic. Two new chemical analyses are given.