This cabochon is actually a doublet. Lab-created optical-quality Quartz covers this perilously thin slice of Variscite. Unfortunately, the Quartz fractured while the glue was curing, so this one is staying in the collection.

Dimensions: 44mm x 22mm x 7.5mm.  Weight: 54.95 carats.

This cabochon is in my personal collection; it is not available for sale.