The minerals here described occur in intimate association with altered pyrochroite, rhodochrosite and zincite, in a vein in normal calcite-franklinite-willemite ore from the Sterling Hill Zinc mines. The willemite in one of the specimens examined, is replaced, near the vein, by brown serpentine (n= 1.56). The cavities in the pyrochroite are lined, and some of the crevices are filled, with glassy white tabular crystals which, upon investigation, proved to be a new mineral, for which the name mooreite is here proposed, in honor of Dr. Gideon E. Moore*, an early investigator of Sterling Hill and Franklin minerals. A closely related bluish-white mineral filling some of the crevices in the pyrochroite is termed here 6-mooreite. The other mineral occurring in the veins is a hair-like material in fluffy aggregates very loosely bound together, filling cavities in the pyrochroite, and covering the crystals of mooreite. Analyses of this material indicate that it is essentially a basic borate of magnesium, identical with the new mineral fluo-borite, recently described by Geijer.1, On one specimen were found some fibrous white rosettes of willemite which resemble the fluo-borite and are easily confused with it.