Classic old material, the Santa Eulalia pyrrhotites are seldom seen on the market today in any quality. Superb, columnar, doubly terminated, pyrrhotite crystals, to 4 cm in length with good luster and a tan color, are partially covered by a druse of calcite. There are even a few lustrous and translucent, colorless fluorite crystals, to 5 mm across, attached to the pyrrhotite - I had not personally seen this association before out of thousands of Naica pieces I have seen since the 1980s. The crust of calcite fluoresces a dark reddish brown when lit in UV. The piece displays well horizontal or vertical