Achtaragdite
available$120
Achtaragdite is a rare pseudomorph of a hydrogrossular-chlorite-carbonate mineral after what is believed to be Helvite. This is a little understood psuedo likely found many decades ago at the type locality for Grossular garnet in Siberia. It is a fine example with a well formed tetrahedron of the form of the former Helvite crystal.