Noted mineralogist Ray Grant dazzled the Arizona Geological Society monthly meeting tonight with an overview of the history, geology, and mineralogy of the Grandview copper mine in Grand Canyon National Park [right, credit Wikipedia]. It was the largest turnout I've seen at an AGS meeting in the past year or more.
The mine started in the 1890's below the Grandview location on the canyon's south rim. The park's first hotel was built there and the mining company may have made more profit from tourism than from mining. The deposit sits in a breccia pipe, with assays running 37% copper. One sample with 70% copper won an award at the 1893 Columbian Exposition.
In 1913 William Randolph Hearst bought the mine and hotel and ran them until selling to the Park Service in 1940.
Ray described 42 minerals found at Grandview, including a few found no where else. Grandviewite is unique to the site and only recently recognized as a new mineral. The pictures he showed of dozens of spectacular specimens explain why the Grandview mine is world-renowned and has been subject to unauthorized mineral collecting over many decades. Bat doors installed in 2009 are keeping collectors out now.
He and his colleagues are continuing studies of the minerals in the mine along with the hydrology and geology in partnership with the Park Service. Ray is also revising his popular Minerals of Arizona book that will include all of these incredible minerals.