Dims: 3.10x2.80x1.92" (7.87x7.11x4.87cm)
Wt: 6.28oz (177.7g)
This specimen is a brown conglomate host rock (brown balls cemented by a soft brown matrix), with a cavity that has been lined with a thin layer of vivianite, plus many long prismatic crystals of viviantite. These crystals are gray-blue and transparent, but their surface luster, while vitreous, gives them a nearly black opaque appearance. The crystals have a cross section and termination rather like a sword. The optical effect is unusual, in that the crystals appear dark and opaque until you hold them up to a light, then they clearly are transparent. Of course, viviantite darkens with exposure to light, so this specimen should be stored in the dark when not on display.