A hemisphere of light gray calcite (colored by minute inclusiosn of sphalerite) is on a matrix of sphalerite and whiteish-gray calcite.The hemisphere, which measures 8 cm across, is actually hollow. The center of the hemisphere has a cluster of calcite crystals with the same grayish color. Fascinating and complicated piece with layers and layers of origin here: a story in mineral "paragenesis," or how sequential minerals and casts of minerals form one after another due to growth and changes in fluiid content over time in the pocket. Mined 2000. Formerly in the Keith Proctor and Scott Rudolph collections.