Achtaragdite is a unique, rare and poorly understood pseudomorph, from this remote Siberian locality that is the Type Locality for grossular garnet. It is a variety of the grossular-hibschite garnet series and is (technically, according to mindat) a hydrogrossular-chlorite-carbonate pseudomorph after what was formerly considered to be wadalite or some other rare hydrogarnet. The real precursor mineral for these pseudomorphs is now considered to be helvite.