This is a large, heavy, museum-sized display specimen of Kelly Mine Smithsonite with the classic blue color that made these famous. While we cannot say for sure when it came out, it probably was in the productive era of the 1960s-early 1980s from the style. The luster is fabulous, the color is perfect, and it just has a shimmering gloss of microcrystals that gives it an unusual sparkle compared to most others, really almost velvety in appearance. It is extremely uncommon to find such large, undamaged specimens of this classic USA material, and this is a fine example for quality, all the more so for the size. From the noted collection of Marty Zinn, who himself lived in New Mexico and built a specialized suite of NM minerals over many years. This is from the deaccession of his Kelly Mine collection, built over decades.