Saturday, December 26, 2009

More Maryland Minerals from Harvard Museum

These days the "haydenite" with "beaumontite" label that accompanies the above picture would read chabazite (in blocky crystals) with heulandite (less recognizable). Haydenite is eponymous with Horace Hayden, an early 18th century dentist, who is credited with its discovery. Early literature depicts haydenite as "a variety of chabazite." Mindat refers to it as a "synonym of chabazite." An easy Internet search reveals a somewhat similar story regarding the nomenclature behind beaumontite/heulandite.

Collected a century plus ago, it hailed from the Harris quarry, one of several long forgotten and filled in filled-in gneiss openings in Baltimore City's Jones Falls Valley. Harvard Mineralogical Museum Curator Carl Francis explained to me in a letter how Harvard obtained this specimen in 1912 as part of the A. F. Holden collection. Holden had purchased it in 1911 for $3 from the legendary mineralogist (and collector/dealer) Lazard Cahn. In his catalog, Holden had described the $3 as "a fearful price for this specimen: bought on Cahn's recommendation." Prettier for sure, but tinier is the chabazite collected here as shown in the micro-photograph at right. It is part of Harvard's vast micromount collection.

Chromian clinochlore is another Maryland piece of note in the Harvard Mineralogical Museum's collection. It's nomenclature is more convoluted than haydenite/chabazite or beaumontite/heulandite. Harvard received both the hand specimen at left and the micromount at right with labels identifying them as nacrite from "Cecil County Maryland near Texas," located just over the state line in neighboring Pennsylvania.

Dr. Francis knew these could not be nacrite, which is a polytype of kaolinite. Because of the locality and purplish red color, he said he would be comfortable labeling them as chromian clinochlore, for which the name kammererite is a synonym. . A more obscure and all but forgotten name for the species is rhodochrome, as referred to in Minerals of Maryland by Ostrander and Price. This book reports rhodochrome both at Bare Hills and Soldiers Delight, also localities in Harford County. In describing the rhodochrome from Maryland's State Line Pits, assuming the pieces shown were collected there, Minerals of Maryland brackets rhodochrome to suggest it's synonymous with penninite. Mindat describes penninite as a pseudo-trigonal variety of clinochlore for which pennine, japanite and miskeyite are additional synomyms. From my photographs, I could not determine whether these crystals were pseudo-trigonal.

I suspect that at one time Harvard's nacrite labels were linked to specimens such as the kaolinite at left. It too, was collected in Cecil County, near Iron Hill, not far from the State Line Pits. Could this particular piece bear nacrite, particularly the brown material at center? The single related reference in the list of Maryland minerals originally sent me by Dr. Francis notes "kaolinite group."

A few other Maryland pieces impressed me as noteworthy. Fred Shaefermyer's flat of Hunting Hill minerals included several rare species including pokrovskite and McGuinnessite. Their photographs are absent here because specimens showing equally well are already in our Maryland Minerals web site's slide shows at Flickr and Picasa. Those slide shows will soon include, however, the Hunting Hill desautelsite image from Harvard's micromount collection as it's shown at right.

Another curiosity from the micromount collection was labeled pharmacolite from the Pinto Railroad Cut in Alleghany County. The 20x photograph at left is insufficient for visual identification. When I first mentioned pharmacolite to Maryland mineral guru Fred Parker, he referred to the occurrence of such a rare arsenate in Alleghany County or for that matter anywhere in Maryland as "just silly." Later after my visit when I emailed him an image, Parker noted that it looked very different from the New Jersey pharmacolite with which he was familiar. The proof, he added would be in an x-ray or EDS analysis, perhaps a worthy undertaking for a Harvard mineralogy scholar.

Another mineral at Harvard I personally had not previously seen from a Maryland locality was vivianite. The substantial specimen pictured at right reached Harvard from an unknown source and was collected at a road cut along Wheeler Road in Oxen Hill, Prince Georges County. The only other vivianite locality I'm aware of in Maryland is a bog at Greenbury Point in Anne Arundel County, where Minerals of Maryland reported an occurrence in grey clay.

Closing out our three post series about The Harvard Museum's Maryland minerals is an example of the species that inspired my original communication with Harvard, namely chromite---in crystals specifically. The micro-photograph at left shows a portion from a hand specimen of Bare Hills chromite from the main gallery cabinet above which a similar looking piece was displayed under glass. Next to the latter had been the glass dish of chromite (actually magnetite) crystals we questioned last summer. The sparkle in this hand specimen enticed me to shoot the macro-photograph at left just before leaving. Regardless of what may or may not have ever been reported of chromite crystals from Bare Hills, this picture suggests their presence. I pass, however, at any attempt to isolate them and place them in a dish.

So there you have it, not only for our Harvard series but for posts during 2009 to the Mineral Bliss Blog. Our best wishes go out to all readers for a happy, prosperous, and wonderfully rocky 2010.

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