Zincite is considered to be a rare mineral, occurring in quantity at only Franklin and Sterling Hill, New Jersey. In its pure form, zincite consists of zinc oxide (ZnO), which is a white colored chemical compound, but when some of the zinc in the structure is replaced by manganese (Mn), the mineral takes on an orange-brown color. Often found in association with willemite, calcite and franklinite at the New Jersey locations, zincite is not usually fluorescent. However, in some cases the zincite shows a moderate yellow response. This example is such a specimen, collected from the Sterling mine in Ogdensburg, Sussex County, New Jersey. This rock consists of orange-brown zincite, grey willemite, white calcite and black grains of franklinite. Under short wave UV the willemite fluoresces bright green and the other minerals show little or no response. Under long wave UV the zincite can be seen fluorescing as small yellow dots and veinlets, while the willemite shows a subdued green response and the calcite glows a dim pale blue. The size of this specimen is 62 x 53 x 29 mm, and it weighs 179 grams.
In the photograph above, taken under long wave UV (365nm), the zincite can be seen as yellow fluorescing dots and small veins. Willemite shows a green response and the dim, pale blue fluorescent mineral is calcite.
Same specimen seen under visible light. The zincite is the orange-brown mineral.
Under short wave UV (254nm), the willemite shows a typical bright green fluorescent response and the zincite does not show significant fluorescence.