The blue color of the Calcite is due to the microscopic inclusion of Graphite. I bought this material at the Syracuse, New York show from some of the club members who had collected it. Only a small percentage of the material has these graphite crystals. This specimen has been acid etched to better reveal the Graphite crystals. The crystals on this specimen are crude and rounded. The largest crystal is 1 cm across, most of the rest are at most half that size. There are also some very thin veins of Quartz which being resistant to the acid have formed raised ridges. There are also a couple of small, pale green pieces of material which were also resistiant to the acid and are now sticking out of the specimen.