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Letters.

MOGUL MINE

Stephen Moreton's article on the Silvermines district, County Tipperary, Ireland (vol. 30, no. 2) was most interesting; I can add some facts about the occurrence of galena and other minerals at the Mogul mine.

In late 1978 I spent a very pleasant couple of days with Dick Barstow, looking through hundreds of specimens from the find. It was a memorable experience. The overwhelming majority of specimens were combinations of galena and sphalerite, with or without drusy iridescent pyrite. Although the fine-grained pyrite looked (and in some cases smelled) suspect, and although some galena crystals had white coatings around their contact with the matrix, it appears in retrospect to be less susceptible to "pyrite disease" than one might have expected.

The sphalerite specimens, reaching 15 cm or so across, consisted of plates of matrix thickly covered with transparent, honey-brown, brilliantly lustrous crystals. Examples bearing reasonably good bournonite crystals were rare, although small and corroded crystals were not uncommon in association with the other minerals.

But it was the galena that I had really come to see, and 22 years later the experience is still vivid in my memory. The specimens were even more spectacular than Moreton's description. Crystals, ranging up to 5 cm (2 inches) or so were as dazzlingly mirror-bright as the smaller crystals. The very finest specimens, of which there were only a few, consisted of single galena crystals disposed on a granular, ivory-white dolomite matrix. Dick kept them in a separate cupboard, and it was easy to see why. I wheedled, cajoled and begged for one, but was too far down in the pecking order. They were destined for Dick's personal collection, for the British Museum, and for a few special customers.

One aspect of the galena not mentioned in Moreton's text (but shown in Fig. 6) is the prevalence of spinel-law twinning. These twins are not as obvious as the flattened twins from Peru, Dalnegorsk and Bulgaria; Mogul mine galena twins are blocky, with only a hint of a re-entrant angle on the twin plane. A few rare examples, such as the one in Figure 6, do show a parallel growth accompanied by some flattening. Barstow had only a handful of such pieces. In my own examples the twinning is clearly delineated by an abrupt change in cleavage angle visible on broken faces. Spinel-law twinned galena is otherwise extremely rare from the British Isles, the exception being the famous Herodsfoot mine in Cornwall, where slightly flattened twins were found in association with bournonite. Corroded bournonite also accompanies the flattened spinellaw galena twins from Castrovirreyna, Peru (is the association significant, I wonder?).

The beautiful dodecahedral sphalerite shown by Moreton in Figure 10 reminds me of one such in Barstow's personal collection. (It may actually be the same one; it's an amazing piece.) Combinations of high-grade galena with high-grade sphalerite were surprisingly uncommon and unsurprisingly expensive!

Michael P. Cooner

Nottingham, England

STOLEN TOURMALINES

Someone broke into an exhibit case at Colby College, Waterville, Maine, and stole many of their finest tourmaline crystals from the Berry-Havey quarry in Poland, Maine. These are superb, terminated, gemmy, emerald-green crystals 2 to 4 inches long, recovered during the early days of mining at Berry-Havey. A large and choice watermelon tourmaline from Newry (another old-timer) was also taken.

Please watch for these specimens in the marketplace, and report suspicious offerings to Prof. Donald Allen, Geology Department, Colby College, ME (tel.: 207-872-3249; e-mail: dballen@colby.edu). Images of similar tourmalines may be seen at: http://www.colby.edu/geology/.

SWEET HOME HISTORY

We debated for probably too long to respond to a portion of the Sweet Home Mine issue written by Steve Voynick on page 20, paragraph 7. The negative reference to Roger and Norm Bennett is both highly offensive and inaccurate. ["In January 1977, Norm and Roger Bennett snowmobiled to the Sweet Home mine on New Year's Day for a bit of underground high-grading... ."] The only thing correct in his description of what transpired is the spelling of our names. A simple telephone call by Mr. Voynick to us would have resulted in an accurate description of how we were involved in a tiny part of this mine's history.

To set the record straight: Norm went to the mine in August 1976 with Mr. Beach. It was on this visit that Norm discovered a nice pocket of rhodochrosite. This pocket was shared with Mr. Beach even though he had initially told Norm he could keep anything he found. Norm and I, along with Mr. Beach, returned on a second trip to try to finish the pocket with Mr. Beach present. Without proper equipment, we were unable to get to the back of the pocket. For reasons known only to Mr. Beach, he did not want to bother with us returning with the necessary equipment to finish Norm's original pocket and splitting 50-50 with him on anything else found. The mine was to be leased the following spring, and we felt it was not right to give the remainder of Norm's pocket to the lessee, so we did not.

Roger and Norm Bennett

Denver and Golden, CO

BEDFORD GEODES

Last summer I revisited the Bedford, Indiana, geode locality (see vol. 22, no. 5, p. 351-354) for the first time in several years. Collecting can still be carried out in the I-37 roadcut. I found no millerite, but did collect some nicely shaped geodes with clear, sparkling quartz crystals. Several also contain nicely developed, pale yellow calcite crystals with rhombohedral terminations. Over the course of about two hours, I and two other collectors gathered 40 to 50 geodes, about a dozen of which are good, keeper display-pieces.

A note of caution: be sure to wear a hardhat at this locality. Although it is aboveground, the productive area of the outcrop has been mined back on the northbound side of the highway, creating a significant overhang. Late winter and early spring freezing and thawing may make the limestone unstable because of cracks opened along joint planes. This will, of course, also render the rock more easily mined by geode-seeking collectors, but do watch your head (this is experience speaking here!).

Rick Ley

West Chester, PA

THE LILY MINE

We have received a number of enquiries regarding the atacamite and gypsum locality (May-June issue cover) known as the Lily mine. Please let your readers know that they can contact us at the mine by fax (51-1-449-8492), e-mail (faro@amauta.rcp.net.pe) or through our website (mineralrt.com/mineperu) (click on the atacamite and selenite).

Felix Rocha

The Lily mine, Peru

NUMBERING SPECIMENS

How should one best number his mineral specimens? I tried to do mine by the Yale and Dana systems but got lost. I asked some curators and dealers, and they said they simply number them sequentially. I have been assigning an arbitrary number to the species (e.g., #184 = Beryl), and then a number for the variety (e.g., #2 = Aquamarine), and finally a sequential number for that variety (e.g., #7 being the 7th aquamarine acquired). So that piece would be #184.2.7. Is there a better system?

Alfred Charman

West Suffield, CT

That depends on how much work you want the number alone to do for you. These days, with computers that can sort huge lists according to any of several data fields, you don't really need to pack so much information into the catalog number.

Cataloging photos of minerals is like cataloging the specimens themselves. I give each of my photos a two-part number, such as 99-10, meaning that it is the tenth photo taken in 1999. So the number carries only date information. But in my computerized database I also give species, variety, locality (in reverse order, e.g., country first, then district, then mine name), owner and specimen size. I could also add a chemical designation (e.g., arsenates). The whole file can be sorted by any of those aspects, whenever desired. So if I suddenly want to see all of the oxalates or all of the Mozambique minerals or all of the microlites I can do so immediately, with a few keystrokes. Complicated numbering systems are really a relic of the years before personal computers. Ed.

THE POETRY OF DECAY

While metallics were never my forte,

I've heard rumblings that cause me dismay,

concerning the nature of sulfides

when near other minerals abide,

causing atoms to and fro to stray.

Is all of this rumor really true,

that sulfur atoms add themselves to

or remove other elements from

minerals in close addendum?

Please inform me what to do.

Can I place galena on display

where non-sulfur minerals do stay?

Will pyrite or any sulfide

cause other mineral atoms to collide

and thus bring forth mineral decay?

Cliff Vermont

Brielle, NJ

There once was a man from Dzhezkazgan who bought all the marcasite that cash can.

But the acid emitted

left his calcites all pitted

Now he's thrown everything in the trash can.

As any curator of an old collection has found, some sulfides do decompose in the drawer, giving off sulfuric acid vapor which attacks nearby specimens and especially paper labels. The worst offenders are marcasite and, to a lesser extent, pyrite, particularly if fine-grained and porous instead of in big lustrous crystals. But even galena will slowly react with the air, as shown by the gradual loss of bright luster over the years.

Ventilation is a useful deterrent to acid vapor damage. If storage is in drawers or closed boxes it's best to keep the marcasites and pyrites segregated. Most other common sulfides probably decompose too slowly to cause a problem. Ed.

ABOUT PHOTOMACROGRAPHY

The article on the crystal morphology of the sodalite family minerals in your March-April issue presented an opportunity for readers interested in photomacrography to think again about techniques. Dan Behnke has pioneered the use of the Olympus Zuiko macro lenses in the United States. Like most American photographers, Dan uses Tungsten films while mineral photographers in Europe often prefer daylight film with blue filters and exposure times up to ten seconds.

I use Olympus equipment too. Vibrations are no problem with long exposures provided that:

(1) The axis bearing the rack of the bellows is supported from beneath. Stacked wood blocks and cartons of variable thickness can do the job. The thinnest cartons of variable thickness can do the job. The thinnest cartons can provide a rough focusing, the final adjustment being achieved with the lens focusing ring.

(2) The nylon gliding channel attached to the central metal track is not damaged. This is very important as the channel can be fissured near its corners where nylon is the thinnest.

When the bellows are extended, there is little space in which to manipulate the fiber-optic tubes for adequate lighting. Though frowned upon by purists, some photomacrographers (including myself) often employ a Vivitar teleconverter. The results can be satisfactory with sufficient practice.

During the last few years, French photomacrographers have developed techniques which yield good results at very high magnifications. Their photographs appear regularly in the French magazine Le Regne Mineral.

Joseph Lhoest

Liege, Belgium

ALUM CAVE BLUFF

It has come to my attention that samples of the new rare earth minerals discovered at Alum Cave Bluff ("The Minerals of Alum Cave Bluff, Great Smoky Mountains, Tennessee" by T. D. Coskren and R. J. Lauf, vol. 31, no. 2) have recently been offered for sale by at least one mineral dealer. I wish to remind readers that any materials collected within a National Park are property of the U.S. Government in perpetuity. In a case like this they are regarded as stolen property and would be subject to confiscation. I also wish to state for the record that neither I nor any member of the staff of Oak Ridge National Laboratory was the source of the Alum Cave Materials now in commercial channels.

R. J. Lauf

Oak Ridge National Laboratory
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Publication:The Mineralogical Record
Date:Nov 1, 2000
Words:1989
Previous Article:Ultimate Standard of Mineral Value.
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