This specimen of classic Kelly Mine Smithsonite has an unusually intense blue saturation to it, slightly more rich in blue than in the typical blue-green-seafoam color we usually see. The surface is built up from myriad bubbles of tiny crystals, grown in clusters upon each other, so it is not a flat coating (as they often are). It is really sparkly as well, with a shimmer to the surface. The piece is simply unusual in form, color, texture, and in the fact that it seems to be made of many smaller "bubbles" joined together, rather than the typical hemispherical growths we see joining up on most other specimens. A unique piece, that stands out from others, from the important New Mexico suite of the Martin Zinn mineral collection (built over many decades). You can see why he kept this one!