Hisingerite is an uncommon secondary, hydrated, iron silicate. Very rare, crystallized plates of reddish-brown, silver metallic-luster hisingerite crystals are festooned on the sculptural matrix of this very rich specimen from the famous Langban deposit of Sweden. Hisingerite specimens are very rare from Langban and this choice piece is from the collection of Dr. Mark Feinglos, a noted rarities collector.