Historic Maryland Mineralogical Epiphany

The specimen pictured above has been sitting around in my office for five years: a mystery mineral. Part of the issue related to a presumably mistaken belief that  it had once been in the company of minerals uncovered during excavation for Baltimore's subway in the 1970's.  No one who saw it ever came close to making a visual identification. For that matter, the matrix looked similar enough to gabbro, that no one ever thought of trying to scratch it

More curious were the radiating crystals: Could they be a zeolite? Aragonite, perhaps?  Of course, had we known the specimen was collected in Harford County or even contemplated that the material was from anywhere other than  the Baltimore Subway Digs, such confusion would not likely have lingered.

To observe the similar specimen pictured at left, in a case at  the Gem, Lapidary, and Mineral Society of Montgromery County's annual show in Gaithersburg, on the weekend of March 15 and 16, 2014, came like an epiphany.  E.M. Bye's historic label identified it as steatite with altered actinolite" from Harford County.
                         
The specimen was in a case of vintage and historically significant Maryland mineral specimens that were  once  part of the world class collection that the Philadelphia Academy had ignominiously stashed away out of sight and devoid of care for decades. Ultimately, in 2007, the Academy sold the collection to several high-end dealers. It was  the most historically  important mineral collection in America and valued well beyond what any other museum could afford to pay.

Mineral Biss was the first to report that Fred Parker had later been able to acquire for posterity most of the collection's Maryland material, which almost surely comprises the most historically significant suite of  Maryland minerals known to exist. Since few of these Maryland-collected pieces had the uniqueness or aesthetic appeal as the kind of specimens in which the dealers who purchased it normally traded, Parker had been able to buy the Maryland pieces for a price that was pleasing to all concerned.

In 2012, after  deciding to downsize his collection and eventually move out of state, Parker contacted Chris Luzier, then Vice-President of Gem, Lapidary, and Mineral Society of Montgomery County about acquiring the suite. That story, with specifics on more of the actual specimens will be the topic of an upcoming Mineral Bliss post.

Meanwhile, can we be certain that this really is altered actinolite on steatite? The steatite, of course, by its softness, is obvious. And while the scientific means of identifying minerals has evolved considerably since E.M. Bye collected the specimen in the 1800's, altered actinolite certainly seems like a good bet.   As for a specific locality in Harford County, it seems extremely likely to have been the Harford Talc And Quartz Company Quarries, as  described in Minerals of Maryland, by Ostrander and Price, published in 1940 by the Natural History Society of Maryland:

HARFORD TALC AND QUARTZ  COMPANY QUARRIES

About one half mile west of Dublin, several large openings have been made in Steatite.  

Minerals to be found are green translucent foliated talc, radiated actinolite, asbestosform anthophyllite, dolomite, calcite, brown vermiculite,  limonite, and calcite in brown phlogopite schist.  

My "mystery" piece is now has a label that states the following: Radiated Actinolite in Steatite from Harford County, Maryland (Probably the Harford Talc and Quartz Company Quarries near Dublin.)