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July-August 2016

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Letters

Geology Museum, Colorado School of Mines, 1310 Maple Street, Golden, Colorado.

Geology Museum, Colorado School of Mines, 1310 Maple Street, Golden, Colorado.

GOLDEN INVITATION

The Colorado School of Mines Geology Museum (CSMGM), in Golden, Colorado, invites all those in town for the Denver Gem and Mineral Show (16–18 September) to attend our annual open house on 14 September 2016, 6–9 P.M., the Wednesday evening preceding the show (whose theme is Minerals of Africa). Come enjoy our displays and visit with our Museum Advisory Council members, student aides, volunteers, and Friends of the CSMGM, and also browse our gift shop. Once again we are offering mineral dealers, corporations, show organizers, and interested individuals the opportunity to help sponsor the event, for which they will receive special recognition in return for their kindness. (Please phone for details; see below.)

Every year we strive to change 20 percent of our exhibits to make our museum more exciting for returning guests. As of this writing (early March), we have firm commitments from Marty Zinn, who has graciously offered to loan us some of his favorite specimens, as well as a display of cut and uncut gemstones from Bob Whitmore, specimens from Ian Merkel, specimens from our Meissner collection, and a display of Colorado calcites from various collectors. Other tentative plans include a display of Canadian minerals, Colorado's most recently verified meteorite, recent acquisitions, and upgrades to our Critical Materials Institute display, and other surprises throughout our museum.

As always, our gala offers free appetizers, a cash bar, and possibly another soothing performance by the melodious Colorado School of Mines String Quartet. We hope to see you there.

REBUTTAL

In the November/December 2015 issue of this journal (pages 582–586) Daniel E. Kile published an impressive argument in support of the probability that Fe-zinnwaldite crystals have occurred in the albite/amazonite pegmatites of the Lake George ring complex in Colorado and elsewhere (Mineral Mysteries: “Hexagonal Hole in Albite and Microcline From the Crystal Peak Area, Teller County, Colorado”). Where he failed, in my opinion, is in attempting to account for the abundant hexagonal holes in the huge amazonite/albite plates collected from the “Key-Hole vug” by Don Smith in 1986 by claiming that these holes were once occupied by Fe-zinnwaldite crystals. It is true that some Fe-zinnwaldite crystals typically have the same shape as hexagonal holes in the feldspar plates, but so did the quartz crystals that were found in a layer below the plates when the latter fell to the floor of the pocket. If memory serves, there were upwards of at least one hundred of these quartz crystals. It was no coincidence, therefore, that there were upwards of one hundred hexagonal cavities observed in the feldspar plates. Not only that, but all of the flattened hexagonal quartz crystals were predominantly similar in size, as were the flattened hexagonal holes in the plates of feldspar. Furthermore, one could actually fit some of the crystals into the holes. What is truly unfortunate is that, although several of the plates were preserved and are in various museums, none of the quartz crystals appear to have been saved.

The photographs that Kile included with his article do nothing to support his position. One shows altered “mica” in cleavelandite that does not have the sharp hexagonal shape of the holes in albite from the Key-Hole vug. The other is a huge zinnwaldite crystal in amazonite about 8 cm in size. None of the holes in the albite from the Key-Hole vug was larger than about 3 cm.

So, if Kile persists, as he appears to do, in insisting that the holes were once occupied by Fe-zinnwaldite, then he has to be able to explain where the quartz crystals covering the bottom of the pocket came from, and he has to discount the fact that they fit neatly into the holes in the albite, the number of which was similar to the number of quartz crystals found beneath the feldspar plates at the bottom of the pocket. In my view the only mystery presented by Don Smith's odd discovery is what mechanism could have caused the quartz crystals to fall out of the feldspar before the feldspar plates themselves dropped upon them. I have no answers.

DANIEL E. KILE RESPONDS

Although I appreciate John White's interest in solving the mystery of the origin of hexagonal holes in feldspars, his letter does not support his assertion that a hypothesis of resorbed mica fails to account for these holes, and he provides no further evidence contrary to this theory.

White has invoked a coincidence of hole shape, size, and number as the only evidence for his argument that quartz crystals once filled these holes. However, improbable coincidences based on personal recollections are not a substitute for physical data and a theoretical foundation of cavity crystallization that could account for that hypothesis.

He claims that the difference in size between micas illustrated in the recent Rocks & Minerals article (November/December 2015) and the hexagonal holes reported from the Keyhole vug does not support the argument that micas once filled these holes. However, his comment does not take into account size differences between euhedral crystals that can grow to relatively large dimensions in an open miarolitic cavity vs. earlier-formed and usually smaller anhedral crystals that are cogenetic with and mostly surrounded by feldspars (both types of which are illustrated in figure 3 in the article), nor does his statement take into account the wide variability in mica crystal size and hole size and shape among pockets. The concluding paragraph in his letter states that the mica theory fails to explain the observed holes for a variety of reasons. Coherent answers to all the issues he raised have in fact already been clearly addressed in the 2015 article, and there is no point in restating them here.

White emphatically concludes that quartz has to have originally filled these holes, but in the absence of physical or chemical data or an alternative mechanism consistent with miarolitic cavity crystallization, there is little to support this concept. He also restricts his hypothesis to only evidence from the Keyhole vug, although the phenomenon of hexagonal holes is common in other miarolitic cavities in the Pikes Peak granite where loose smoky quartz crystals have not been found. In contrast, the hypothesis that mica crystals had originally filled these holes is backed by field observations, compositional data, and a plausible mechanism for mica dissolution.

2015 SALOTTI AWARD

The Michigan Earth Science Teachers Association (MESTA) and the A. E. Seaman Mineral Museum are honored to announce that the 2015 Charles A. Salotti Earth Science Education Award recipient is Dr. William “Bill” Rose of Michigan Technological University. Rose was formally presented with the award at the MESTA fall conference banquet held 9 October 2015, at Okemos High School, in Okemos, Michigan.

The Salotti Earth Science Education Award has been presented annually since 1999 by the A. E. Seaman Mineral Museum to recognize individuals who have made outstanding contributions to earth science education. Beginning this year in partnership with MESTA, the award now focuses on recognizing excellence in informal earth science education and/or mentoring.

Rose has had a distinguished career as a researcher and educator on the faculty of Michigan Technological University since 1970. Now as professor emeritus in the Department of Geological and Mining Engineering and Sciences, he has given tremendous effort toward informal earth science education. MESTA's Salotti Award selection committee was impressed by the letters of recommendations from colleagues as well as current and former students who cited numerous examples of Rose's recent work, including developing geoheritage programming and embedding geoscience of the Keweenaw area within community partnerships and projects, initiating geological interpretive signage within the region and on the Michigan Tech campus, working with teacher professional development outreach programs to promote the “Big Ideas of Earth Science” in the Michigan Teaching Excellence Program, and frequently offering educational public lectures and field trips.

Nominations for the 2016 award are now being accepted. For nomination details and a downloadable form, please visit MESTA's awards and grants website at https://www.mestarocks.org/cms/content/grants.

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