Lautite is a relatively rare sulfosalt and occurs nowhere more abundantly, or in more attractive combinations specimens, than at El Gallito, Mundo Nuevo Mine, Peru. Dr. Frank Keutsch (Harvard mineralogist and mineral collector of rare sulfide species) acquired and studied many fine pieces of the material and this one represents the most dramatic of all of them, in his opinion possibly the richest specimen known in display quality with a world-supply of lautite crystals atop. A trio of very large, perfectly formed Tennantite crystals to 7.5 cm are heavily sprinkled with hundreds of gray-black, metallic, sub-1 mm Lautite crystals. The piece is nicely accented by a 4.4 cm, colorless to slightly milky Quartz crystal that peeks over the top of the Tennantite trio and has several small, 1 cm Quartz crystals growing off perpendicular to it near its base. Lautite's formula very straightforward, CuAsS, and is very similar to Tennantite. This is an impressive and unique combination specimen from the Mundo Nuevo Mine. Ex. Frank Keutsch personal collection (and he also did the x ray work to confirm it in 2017 - noting on the back of his label : best combo, rich lautite on largest tennantite). 456 grams. A significant specimen that might just be best overall of species.