A rather standard sample of northern New Jersey zinc ore, with abundant black franklinite crystals and red-brown zincite in a massive calcite matrix. This specimen is a bit different as two faces bear drag or friction marks (slickenside). Wikipedia defines this as "a smoothly polished surface caused by frictional movement between rocks along a fault. This surface is typically striated with linear features..." The specimen also displays fluorescence typical of this material: under longwave UV the calcite glows a dull red and the willemite is bright green. Under shortwave UV (shown in the photos) these colors are much more brilliant. Curiously, the fluorescence is muted or even completely gone along the slickenside faces. Self standing.