Fine-grained secondary calcite containing numerous tiny needlelike crystals of willemite, best visible under shortwave UV. The gray granular mineral on labeled face is dolomite, and the black mineral rimming some of the clasts is probably pyrochroite. A fine example of this type of specimen. Should examine this specimen closely under longwave UV. In some specimens of this type, the calcite glows green LW where it is intergrown with abundant willemite. As the willemite content decreases and calcite increases, the fluorescence changes to yellow, to orange, and then to red, depending on the willemite:calcite ratio. Such specimens can be visually striking under longwave UV.
Value is dependent on long-wave fluorescence, perhaps $800. A similar specimen recently (late 2011) sold for $2,000.