Canyon Sketches Vol 25 - May 2012

Grand Canyon's Museum Collection Curates Rare Minerals from Grandview Mine
The mineral grandviewite is only known from Grand Canyon
Allyson Mathis

 

Photo of Grandview mine in operation.

Grand Canyon Nat. Park Museum Collection #08808

Grandview Mine, located three miles below the South Rim of Grand Canyon on Horseshoe Mesa, is perhaps most famous for its rich copper ores that won a contest at the 1893 Columbian Exposition (World's Fair) in Chicago.

The mine's ore was assayed at more than 70% pure copper. While all mining-related activities ceased by 1907 after the price of copper collapsed, the former mine remains of great scientific value because of its assemblage of rare minerals, including grandviewite.

Grandviewite, a turquoise-colored mineral known only from the Grandview Mine was not formally named and described until 2007.

 

In 2010, more than 1,200 mineral specimens from Grandview Mine were added to the Grand Canyon National Park's Museum Collection. Geologist-in-Park Janelle Rohweller identified and cataloged these specimens last summer during an internship through GeoCorps America.

 

Miners working in Stope B, 4th level (1906)

Grand Canyon Nat. Park Museum Collection #08805

Pete Berry and partners developed the Grandview Mine from two mining claims filed in 1890. The Grandview Trail was built in 1892-1893 to service the mine to haul ore out of the canyon by pack train.

The ore consisted mostly of copper sulfate minerals including cyanotrichite, brochantite, and chalcoalumite, along with copper carbonates such as azurite and malachite. Like many historic mines in Grand Canyon, including the Orphan Mine, the mineralized zone is in a breccia pipe, which is a cylindrical mass of highly fractured rock.

In the Grand Canyon region, breccia pipes formed from the collapse of solution caverns in the Redwall Limestone. The highly porous brecciated rock in these features was mineralized by copper- and/or uranium-bearing fluids.

 

Bat gate installed during 2009.

nps science & resource management photo

The old mining site on Horseshoe Mesa is marked today by the remains of a stone cook's cabin and other structures and several partially collapsed openings into the former mine.

In 2009, the National Park Service, with the support of Bat Conservation International, installed bat gates in three adits to prevent people from entering the hazardous mine while still providing access for Townsend's big eared bats who use the Grandview Mine as a nesting colony site.

Additional closure work was accomplished in 2010 under funding provided through the American Recovery and Reinvestment Act (ARRA).

Abandoned mineral lands pose significant hazards to human health and safety because of the risk of collapse, rotting timbers, and other dangers.

 

Grandviewite specimen GRCA #108407

NPS Photo by Michael Quinn

Grandviewite is a light blue-green mineral that occurs in small tuffs of radiating needle-like crystals. It had been described as an unknown mineral in 1971 by a mineralogist who had a research permit from the park, but it wasn't until 2007 that it was described as a new mineral species accepted by the International Mineralogical Association. Grandviewite has a chemical formula of Cu3Al9(SO4)2(OH)29. It grows in close association with other copper aluminum sulfate minerals such as chalcoalumite and cyanotrichite.

More than thirty ore minerals for copper, zinc, lead and uranium have been identified from the Grandview Mine by researchers. A number of the minerals found in the Grandview Mine are rare, including the only known occurrence of philipsbornite in North America.

 

Geologist-in-Park Janelle Rohweller

nps photo by Allyson mathis

The GeoCorps America Program supplied support and funding for Geologist-in-Park Rohweller to inventory and catalog the specimens from the Grandview Mine that the Museum Collection obtained during recent years. GeoCorps America is a program of the Geological Society of America in partnership with the National Park Service and other federal land management agencies.

Grand Canyon Physical Science Program Manager Deanna Greco said, "GeoCorps America enabled the park to identify and describe these specimens. It was great to bring someone onboard with mineralogical expertise and have them be dedicated to cataloging these specimens.

 

Geologist-in-Park Janelle Rohweller

NPS photo by allyson mathis

The rare minerals from the Grandview Mine are just one of the diverse geologic resources in Grand Canyon in addition to the incredible scenery and vast record of geologic history. It is important that we inventory, monitor and protect all geologic resources in the park, including minerals, springs, fossils and caves."

In order to not damage the samples, Rohweller identified them on the basis of macroscopic appearance and description from the literature. Rohweller said, "The most challenging aspect of my internship was the actual identification of the minerals. The rareness of some of the minerals made them difficult to identify since very little information was available on their characteristics. This issue was compounded by the fact that many samples were very small."

 

(Top) parnite & other (bottom) azurite & malachite & cyanotrichite.

NPS PHOTO BY Michael Quinn

Because several methods for mineral identification are inherently destructive, Rohweller was not able to definitively identify all mineral species included in the Grandview Mine specimens. There may be additional minerals new to science, including possible arsenate minerals, among the collection. These samples, which include at least 18 specimens that contain grandviewite, are part of the permanent curation at Grand Canyon National Park's Museum Collection.

While Grand Canyon is most famous for vast views of towering cliffs, it holds additional geologic treasures, some as tiny as the delicate blue-green needles of a grandviewite crystal.

View more photos of the mineral specimens here:

For more information on GeoCorps America: http://rock.geosociety.org/g_corps/index.htm

Download Quest For The Pillar of Gold (22.5 MB PDF file) a Grand Canyon Association monograph about mining and miners of Grand Canyon.

 

Note: Collection of, unauthorized removal, possession of, and sale or commercial use of rocks, minerals, and paleontological specimens, for either recreational or educational purposes, is generally prohibited in all units of the National Park System (36 C.F.R. § 2.1(a)). Violators of this prohibition are subject to criminal penalties. Anyone with information about illegal activities or who would like to report suspicious activity in Grand Canyon National Park should call 1-928-638-7805. You may speak directly to a criminal investigator or remain anonymous when reporting these activities.

References:

Colchester, D. M., Klish, D. R., Leverett P., and Williams P. A., 2008, Grandviewite, Cu₃Al₉(SO₄)₂(OH)₂₉, a new mineral from the Grandview mine, Arizona, USA: Australian Journal of Mineralogy, v. 14, p. 51-54.

Leicht, W., 1971, Minerals of the Grandview mine: The Mineralogical Record, v. 2, p. 214 - 221.

 

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