Milpillas in Mexico is a modern copper mine that has produced a shocking amount of azurite from around 2008 onwards, combined with occasional surprise bursts of world class crystals of otherwise very rare species. It is always a surprise when something new comes out, and people rush to get the x-ray done to see which old species of copper mineral has been surpassed for crystal quality (brochantite, then volborthite, olivenite as you see here...). Azurites are common enough but this kind of mineral is always rare and never comes in big finds. We had seen small olivenites of no consequence, and then this pocket turned up on the 992 foot level, and produced amazing sharp textbook crystals of olivenite. The largest I am aware of was 2.5 cm, and this thumbnail, balanced and pristine, shows off a 2 cm vertical tower of perfect olivenite. It is a world class thumbnail of the species. Please also note that most world class large crystals we know as TSUMEB olivenites are in fact, not... technically they were reclassified and named to zincolivenite.