Thursday, July 19, 2018

Baltimorite


Pictured above is a specimen of serpentine collected circa 1940 at the chromite bearing serpentine barrens of Bare Hills in Baltimore County, Maryland. It is one of several such specimens The Natural History Society of Maryland owns. Very likely Charles Ostrander and/or Walter Price, the Society's  prominent curators at the time, collected them. The NHSM labels identified the specimens as  "baltimorite". Minerals of Maryland, the NSHM publication that these two curators co-authored in 1940, may have been the last regional publication to suggest that "baltimorite" was  a species or variety of a species.

 Mindat describes  baltimorite as a "synonym for antigorite." along with 11 other names including "gymnite" and "porcellophite." Interestingly, Minerals of Maryland refers to "gymnite" and "porcellophite" as separate minerals that also occur,  along with "baltimorite," at Bare Hills.  The three names  have since all but disappeared from mineralogical parlance, although  Bernard and Hyrsl's Minerals and Their Localities refers to gymnite as a synonym for deweylite,  which is typically identified as a mixture of several varying different species that can occur  together at some of central Maryland's serpentine outcrops.

In addition to naming twelve antigorite synonyms, Mindat also names eight varieties of antigorite. Two of them, williamsite and chrome antigorite,  are known to those who collect in the serpentinized areas of Central Maryland and Southern Pennsylvania. Highly valued  in lapidary circles, williamsite is  best described as a  solid and translucent apple-green antigorite included with specks of black chromite. Chrome antigorite displays varying amounts of reddish purple coloring attributed to the presence of chromium. It is usually columnar or fibrous and known to occur primarily at the now off-limits Woods Chrome Pits in Lancaster County, Pennsylvania  just a few miles north of the Mayland state line.   

Antigorite, lizardite, and chrystotile are the best known of 13 species in the serpentine subgroup. In addition to these 13 species, the serpentine subgroup as an entity boasts eight varieties, none of them approved as species in their own right.

 One such serpentine subgroup varietiy is picrolite. Mindat defines picrolite primarily by habit  as "a columnar or coarsely fibrous (non - asbestiform) variety of serpentine commonly referred to as a variety of antigorite, but may be other species." The most common of these "other"  species are the serpentine subgroup mineral species lizardite and chrystotile. Picrolite is ubiquitous at nearly all the serpentine exposures in central Maryland and southern Pennsylvania. Note the label on the NHSM specimen at right : "Serpentine, var. baltimorite (Picrolite). It makes sense. Here it can be assumed that the term picrolite was used to to refer to the columnar habit of the sample.  The original material that was given the name baltimorite in 1843  and  wherever else the name was used thereafter matched the Mindat description of picrolite. Typically the color of picrolite is green as shown in the image at left. Interestingly the color of  the several "baltimorite" specimens at NHSM---which are the only specimens anywhere so labeled that we are aware of--- is  brown.  Would it be unreasonable to colloquially refer to picrolite of brown color as "baltimorite?" An interesting aside is that the approved species known as "chrome antigorite," like picrolite, is almost always columnar.

It was Thomas Thomson, a British mineralogist, who came up with the name baltimorite in 1843 (Phil.Mag.22, 1911). He had recently received a specimen from the well-known American scholar and collector Francis Alger. Collected at Bare Hills in Baltimore County, the specimen was opaque with a silky luster and consisted of longitudinal fibers that adhered to each other. Alger had referred to the material as "asbestos and chrome."Thomson studied the specimen. After ruling out the presence of asbestos as well as chromium, he named it baltimorite for the locality.

Two  years later, citing Peggendorff's Annals, Vol. lxii, p. 137, The Edinburgh New Philospophical Journal, Volume 39 published in an article that the German mineralogist Karl Friedrich August Rammelsberg had found that Thomson's "baltimorite" was identical  to other material that had  become known as chrysotile by Kobel.  Franz Kobel  was another German mineralogist, who had originally called the material Schiller asbestos. The conclusion: "As the latter (baltimorite) was described subsequently to the former, the name of baltimorite must be given up."

However, the baltimorite handle endured, only to receive an additional blow in 1855 by a supplement to Dana's The System of Mineralogy. Therein it was noted that two years earlier,  the German mineralogist C. von Hauer had published a new analysis of purported baltimorite in which the chemical composition varied from the original composition given by Thomson. The Dana supplement concluded: 
We have a new analysis of a stone which somebody has labeled baltimorite. It is very wide from the original baltimorite of Thomson (from Bare Hills, Maryland) and is no better entitled to the name than many other fibrous stones that could be gathered from our serpentine regions.
 Eighty one years later in 1936, the American Mineralogical Association placed the final nail in "baltimorite's" coffin. The American Mineralogist in an abstract of a paper by George C. Selfridge, Jr.  of Columbia University entitled "An X-ray and Optical Investigation of the Serpentine Minerals" proclaimed on page 463:
Based on the results of the x-ray and optical studies and the chemical discussion---to drop the names picrosmine, picrolite, williamsite, bowenite, porcellophite, and baltimorite  for the term antigorite. The term serpentinite is suggested for rocks composed of serpentine or antigorite or a mixture of both. 
The recommendation came at about the same time as the mineral aficionados at NHSM were collecting and labeling "baltimorite" specimens from either Bare Hills or the geologically similar Soldiers Delight serpentine outcrops, also in Baltimore County. Interestingly, the NHSM labeled as "picrolite" numerous specimens from serpentine outcrops in Maryland's  Harford County that appeared to differ from those labeled "baltimorite" only by their green color.

Then in 1956, in Vol. 41 of  The American Mineralogist,  a 21 page paper by George T. Faust and Bartholomew Nagy outlined studies showing "that minerals classified as serpentines are either chrysotile,  antigorite, or natural mixtures of these two minerals--- It is suggested that serpentines should be redefined in terms of the relative proportions of antigorite and chrysotile"

Notwithstanding, the endless questions, answers, and names involving  various species and varieties in the Serpentine Subgroup have continued---and undoubtedly will continue--- to evolve without reference to baltimorite  For now, here is the best definition for baltimorite we've been able to come up with:  an obsolete and antiquated synonym for picrolite, a serpentine group variety, which depending upon composition may actually be antigorite, lizardite, chrystotile, or a combination of them.

We are grateful to John S. White, Past Curator in Charge of the Mineral and Gem collection at the Smithsonian's National Museum of Natural History for suggesting this story, turning us on to some of the referenced sources, and proofreading it. 
  

Wednesday, March 7, 2018

Leesite: Another New Species Discovered by Patrick Haynes


Leesite

Patrick Haynes
In  1989, Patrick Haynes collected what 27 years later would become the new uranyl oxide micromineral leesite. Its locality is the Jomac Mine in White Canyon, San Juan County, Utah.  It is the locality, where at about the same time, Haynes  discovered two similarly rare and microscopic uranium bearing species, blatonite and oswaldpeetersite.   The name leesite is eponymous with Brian Lees, the legendary owner of Collector’s Edge.

Soon after collecting it, Haynes examined material under the microscope and assumed that it should be an identifiable species. The orange color led him to suspect it to be fourmarierite or curite. He submitted it to Dr. Michel Deliens at the Royal Belgian Department of Natural History in Brussels, Belgium along with other material, which the International Mineralogical Association (IMA) would later approve as blatonite and oswaldpeetersite.  The verdict on the future leesite suggested that it was a combination of species.

Ten to fifteen years later, Haynes learned about success at identifying difficult new species by  Dr. Frank Hawthorne, Professor of Mineralogy and Crystallography at the University of Manitoba.  He sent a sample of the orange unknown material to Dr. Hawthorne to examine. Like the scientists in Brussels, Dr. Hawthorne believed it could be a mixture, but this time of a different combination of minerals.   

Haynes  explained:

Leesite is very fine-grained, and it is commonly associated with another orange potassium uranium oxide called compreignacite, which can make sample preparation very difficult. With the few "coarser" crystals one can generally make a visual determination, but that is unusual.

A few years later Pat became aware that Travis Olds and Tony Kampf had been “working up these ridiculously tiny minerals from Utah.”   Around that time, Haynes encountered Dr. Peter Burns from University of Notre Dame, under whom Olds had studied when earning his PhD. He sent samples of the questionable material to Dr. Burns and PhD students to study. Dr. Olds, now a post-doctorate researcher at the University of Washington and his associates produced a successful and convincing analysis. Then Tony Kampf and several other mineralogists provided further input. The result was the submission of an abstract to the IMA for approval  of a new species, to be named leesite. The approval came in 2016.

IMA rules stipulate that approval of a new species becomes official only after the authors of the abstract seeking that approval have published a synopsis. That happened in January, 2018, when the American Mineralogist published a synopsis of leesite by Olds, Kampf, et al. Patrick Haynes believes that only 130 samples of leesite are known to exist.  All of them, were collected at the Jomac Mine, which was reclaimed in 1992, and leesite has been reported from no other locality on earth.

Thursday, February 8, 2018

Alfredo Petrov and an Opal Sulfur Dilemma


Something is different  in Tucson this year. Alfredo Petrov and his inventory of  mostly unusual specimens with precise handwritten labels are  nowhere to be found at the Inn Suites. Nor will he be doing the big show. Instead,  he is among a small group of  wholesale and retail dealers with interesting minerals in the JTI tent at La Fuente de Piedras, 1535 North Oracle.

Here as at the Inn Suites, Alfredo holds forth about minerals with  a diverse stream of connoisseurs, cognoscenti, and the simply curious. More often than not, the topic relates to specimens he is selling. It seemed odd when he picked up from amongst those specimens a small cabinet specimen of native sulfur crystals. Their locality was the El Desierto Mine in southwestern Bolivia. These crystals seemed at first an unlikely pick for Alfredo, a dealer of minerals that are less common.  Nearby, a Jewel Tunnel Imports table was completely covered with similar pieces.

Alfredo acknowledged that that it was the bright yellow color of these and all native sulfur crystals that attracted most collectors. Except for certain uranium bearing minerals, not many easily acquired species  can compete with them in terms of brilliance. He recalls when his mentor, the late mineralogical icon Rock Currier instructed him: "Alfredo, I'm going to teach you the three secrets to success at selling minerals. They are #1 color; #2 color; #3 color." Interestingly, Currier was the first  to bring  El Desierto Mine sulfur crystals to the US. He imported about 15 tons of them.  Over the last decade, other dealers have imported another five or so tons. The market for these beautiful crystals is endless.


Alfredo's interest, however, goes beyond the color. He points to the white transparent material atop some of the crystals. It is hyalite opal. Viewed from a distance, its presence makes the crystals  seem less distinct, even less brilliant. Alfredo explains:
"What's important is that the sulfur forms from volcanic fumarole fumes. The sulfur is in the gas, and the crystals grow out of the gas. There is no liquid involved as there is when most minerals form. If the hyalite opal formed volcanic gases, where could the silica be in that gas? Opal is derived from quartz, which doesn't evaporate, so you don't get siliceous gas. 
He continues:
"The melting point of sulfur is 108°C. The presence of the hyalite proves that the temperature of opal deposition. was 108°C or less. If the opal had ever reached that temperature, the sulfur crystals would have been melted. "
 Alfredo then points to a larger specimen where a small amount of the sulfur is black in color. He notes that analysis has shown the black material to be covellite, a copper sulfide. This occurrence raises a similar question. The type locality for covellite is Mount Vesuvius, which demonstrates its potential for volcanic origin.

Metallic sulfides formed  as volcanic sublimates are rare albeit explainable. But how does one explain the  presence of silica in any any kind of volcanic sublimate? Despite his legendary knowledge of minerals, Alfredo does not have a sure answer.

"There is a well-known theory among volcanologist," he notes, "that silica is trasported by HF (hydrofluoric acid), a very, very, very nasty gas, which transports silicon as SiF4 (silicon tetrafluoride)."

Alfredo spends considerable time field collecting in volcanic regions, especially in Japan. And then:

"If this is true, then spending much time breathing around  volcanic fumaroles would be a very unhealthy experience, and I'm going to die a nasty death."

Let's hope it isn't true, and there's a different chemical mechanism we don't know about yet.


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