Cave Boxwork Mineralization Section
Caboolture, Queensland Austraila
General measurement: 25 cm; no weight given

A mineral formation of travertine, calcite, and possible quartz of a dolomite cave environment. Essentially this is a ​raw unfinished ​section of marble. The ​formation is called "Boxwork" and is considered a "drip stone"​; one of many cave formations that include cave stalactites and stalagmites. It takes an incredibly long time for these formations to develop and this example could be older that 5 to 10 millions years. Boxwork is a unique cave formation characterized by thin blades of calcite that project from cave walls and ceilings, creating a honeycomb-like pattern. The geometric voids in the formation are due to dissolution of pyrite crystals. Pyrite is an iron sulfide, and can oxidize to iron oxide (rust), which is soluble, leaving the voids behind.

I am unable to find a similar example sold at auction; but it is a common example that is often found in retail geology stores and at gen and mineral shows. Looking on gem and mineral auction sites could lead to more information on this example.