Crystallized cyanotrichite of this quality is incredibly rare worldwide! One of the best locales known is this small mine worked in intervals in the copper boom of the late 1800s and into the early 1900s, halfway down the depths of the Grand Canyon in what today is a National Park (no more collecting! no more dynamite!). These old specimens, collected long ago, are very rarely seen back on the market. This actually is the largest and richest overall specimen I have personally handled, and do not know of but a few of this caliber even exist. Ex. Bob Bartsch collection. From Wikipedia: The Grandview Mine, also known as the Last Chance Mine, was operated by Pete Berry from 1892 until 1901 in what later became Grand Canyon National Park. The Grandview Mine Historic District includes what remains of the mine workings and machinery as well as the ruins of a stone house and sleeping shanty. Physical evidence, including low stone walls and construction debris, suggests that several wood structures were also originally present on the site. Pete Berry established Last Chance Mine on Horseshoe Mesa in 1892. He constructed the four-mile Grandview Trail down to the copper mine, and in 1893 began hauling ore out by mule. Although the ore was over 70% pure copper and won a prize at the Columbian Exposition in Chicago, the mine did not prove profitable, and in 1901 Berry and his partners sold it to the Canyon Copper Company, who operated it until 1907. The mine was then acquired by William Randolph Hearst, who sold it to the National Park Service in 1940.