This is an excellent specimen of AZURITE from the Milpillas Mine, near the town of Milpillas, in the Cananea District, Sonora, Mexico. The rich, navy blue color is typical of the top notch specimens that come from this locality. Milpillas is a copper mine which opened in early 2007. It produced a few hundred good specimens in late 2007, and they have been displayed at subsequent Tucson Gem, Rock & Mineral shows, often selling for ridiculously high prices.

When Industrias Peñoles opened the mine in 2006, they reported that the expected life was 11 years. However, the upper oxidized zone was exhausted in early 2012. A new pocket was discovered in late 2013 in a crevice in the cuprite ore below the oxidized zone, and many of these were on display at the 2014 Tucson. All Milpillas specimens have had to be smuggled out of the mine. According to a recent report , after the mine owners heard about the new pocket, they had the walls sprayed with cement to stop illicit collecting.

To sum this situation up, mineralogist Peter Megaw said that, "In 10 years these will be hard to find classics... so load up now while you can!" Thomas Moore added that "…collectors thus are advised to choose their Milpillas "keepers" without too much dithering."

Many of the best azurite specimens from the locality show a distinctive electric blue color which stems from an interesting paragenesis. These specimens first grew as azurite which was pseudomorphously replaced by malachite and then covered by a later growth layer of azurite. It appears that light reflects off the malachite underlayer and back through the outer azurite layer to create the distinctive color.