This rich piece has protected vugs all over it with sharp, lustrous crystals of jarosite. One of two extremely rare specimens of jarosite, a complex iron sulfate, from the world's richest cassiterite-mining deposit. This is one of two specimens apparently found together and retrieved during (going by the number system) the 3rd or 4th Vaux expedition to Bolivia in the late 1930s. Comes with original label from the Vaux collection at the Academy.