These strange replacement pseudomorphs are extremely rare, and usually rather unattractive and dull. This, however, is a rather elegant cluster of stark white, sharply hexagonal witherites that have been replaced by barite now. These are old specimens , generally 19th century and early 1900s material. Seldom do you see even a reference example for sale, let alone such an aesthetic, display-quality piece. Formerly in the collection of noted US collector, Phil Scalisi

Once considered its own species, this sphaerosiderite is now considered to be a microcrystalline, botryoidal variety of siderite. It is classic and unique material, though, and comes at its best from this old mine in Romania. This specimen is complete all around, and is a gorgeous and rich example of both the species variety, and of the classic association from this particular mine. I have seen these pop up from time to time in old collections, but never one so good as this one.