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September-October 2009

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Letters

GOLDEN INVITATION
The Colorado School of Mines Geology Museum, in Golden, invites all those in town for the Denver Gem and Mineral Show, 18–20 September, to attend our annual open house on 16 September, 6–9 P.M., the Wednesday evening preceding the show. Come meet some of our museum advisory council members, student aids, and volunteers and also see our gift shop (new since last year) and ever-evolving collection.

Of special interest this year, the Johnson Space Center has granted us the long-term loan of a lunar basalt specimen from Apollo 15. We hope it will arrive in time for the festivities. If all works out, it will be part of an interesting exhibit comparing terrestrial and lunar basalts, making us the first university science museum in the country to feature such an exhibit.

New displays erected this past summer feature Climax, the world’s first molybdenum mine; pyromorphites from the John Marshall collection; trilobites from the Dan Unruh collection; a celebration of the 150th anniversary of the Colorado Gold Rush; a vastly improved ultraviolet display; an indepth look at the Cripple Creek mining district; and delicate speleothems from the Clear Creek Cave in Jefferson County, Colorado. Also new is a phenomenal pyrargyrite specimen, from Fresnillo, Zacatecas, Mexico, donated by the Oreck family. Its crystal size, perfection, luster, and pedigree make it a top specimen for the species. Further, we hope to have newly designed labels near each of the specimens throughout the museum.

No bash is complete without complimentary hors d’oeuvres, a cash bar, and a silent auction, so look for those as well. The incredible Colorado School of Mines String Quartet (minus one musician, therefore a trio) will be performing. Do stop by and join us.

Bruce Geller, Director
Colorado School of Mines
Geology Museum
Golden, Colorado

The pyrargyrite from Fresnillo, Zacatecas, Mexico, donated to the Colorado School of Mines by the Oreck family. The specimen is 16 cm across. Richard Jackson photo, courtesy Collector’s Edge.

The MICHIGAN COPPER CRYSTALS
In the article “A 2008 Bonanza of Copper Crystals, Keweenaw County, Michigan” that appeared in the January/February 2009 issue, I mentioned the possible occurrence of “octahedral” copper crystals that were recovered from the pocket. What appeared to be octahedra, by visual examination, occurred as single crystals that capped elongated growths of dendritic crystals. Shortly after the discovery, a preliminary study of the crystals was done by Dr. George W. Robinson and Dr. John A. Jaszczak. They determined that the crystals may show a “pseudo-octahedral” habit, but from preliminary goniometer measurements, the crystals were probably dodecahedra. In a follow-up examination, several crystals were sent to Dr. R. Peter Richards by Bob Barron for examination; the following is his reply that leaves no doubt that they are dodecahedra:

The ends of the crystal groups often are terminated by four faces at equal angles to each other. These could be the top faces of an octahedron, as initially believed, but they could be four faces of a dodecahedron. In either case, one of the fourfold axes of the isometric system lies in the middle. The difference between these two forms is in the angles between the faces. Perhaps the easiest one to visualize is the angle between a face and the face diagonally opposite it. For the octahedron, this angle is 109 degrees 29 minutes; for the dodecahedron, it is 90 degrees (according to crystallographic convention, an interfacial angle is given as the angle between lines perpendicular to each face. Consequently, even though the faces of the octahedron are “steeper,” the interfacial angle is larger). Measurements of several crystals with the twocircle goniometer show that the angle is indeed 90 degrees, establishing that the form is the dodecahedron. Additional faces of the dodecahedron are present in some cases. On other crystals, the dodecahedron is modified by the trapezohedron {012} and/or an unidentified hexoctahedron.

Tom Rosemeyer
Magdalena, New Mexico


The AFMS HONOREES

The honorary award winners for the American Federation of Mineralogical Societies (AFMS) Scholarship Foundation have been selected by their federations for 2009. These honorees are being recognized for their outstanding contributions to the Earth science field. Each will choose two deserving students who are pursuing advanced degrees in the Earth sciences to receive scholarship grants from the foundation of $2,000 per year for two years.

The honorees are as follows:
California Federation—Jeane and Bob Stultz, Redding, California.
Eastern Federation—Dr. Michael Brown, University of Maryland.
Midwest Federation—Dr. Raymond R. Anderson, Iowa Geological Survey.
Northwest Federation—Dr. David A. Lopez, Montana Bureau of Mines and Geology.
Rocky Mountain Federation—Prof. Steven W. Veatch, Colorado Springs, Colorado.
South Central Federation—Jean Wallace, Temple, Texas.

Dee Holland, President
AFMS Scholarship Foundation
Tendoy, Idaho


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