Forty sphalerite samples from the Star mine, Coeur d'Alene district, Idaho, and 19 sphalerite samples from other Coeur d'Alene mines have been quantitatively analyzed by spectrographic methods for Fe, Cu, Pb, Cd, Ga, Ge, In, Mn, Co, and Hg. The samples from the Star vein were collected over a strike length of 2,000 feet and a vertical distance of 5,300 feet.It is believed that Star mine sphalerite formed in equilibrium with Fe; consequently, following Kullerud's work, the Fe content may be used as a relative temperature scale. Relative Fe temperatures suggest that the lower portions of the Star ore body formed at lower temperatures than the upper portions of the ore body.Distribution of the minor elements in sphalerite is random within the ore body. Also, there is no correlation of Fe with minor elements other than Mn; therefore we believe temperature has had no influence on the distribution of minor elements, except Mn, in this ore body.The principal reason for this seems to be that equilibrium concentrations of the minor elements were not reached. Minor-element concentrations in sphalerite from the Coeur d'Alene district are similar to those in other districts throughout the world; consequently, the writers suggest that in general the minor-element content of sphalerite, other than perhaps Mn, cannot be an indicator of formation temperatures because equilibrium concentrations are rarely, if ever, attained.The average minor-element content in a district is probably that of the ore-forming solutions. Specific minor-element content in sphalerite is random.