A fine combination specimen from Naica, Mexico. Lustrous, black sphalerite crystals to 2.7 cm with superb trigonal growth faces are aesthetically set on matrix with glassy, colorless, cuboctahedral fluorite crystals and a well-placed, 2.7cm, partially skeletal, galena crystal. Seldom do you know the exact mine from this famous district. However, this Mullane Collection specimen comes with a University of Sonora Engineering School label that tells us the mine, which is very uncommon - the Siglo XX.