Barium is one of the rarer metals to acquire for the collector. The main problem stems from its very reactive nature that makes it very difficult to keep it from oxidizing. The difficulty in reducing the metal from the ores as well as the lack of a substantial market for barium in elemental form make difficult to acquire and expensive.
As is the case with the rest of the reactive metals on offer in these acrylic boxes, we embed the samples in an inert, immobile gel to preserve the integrity of the sample. Small bubbles present may clear up on prolonged exposure to direct sunlight.