Friday, July 1, 2011

A Staurolite Find Near Baltimore

Without specifying staurolite, we heralded Bob Simonoff's find along Jones Falls near Rockland in Baltimore County, in the March 27, 2011 Mineral Bliss post entitled A Mineralogical Hike Near Baltimore, Maryland. Later, in our most recent post , Cummingtonite, Amphibole-Anthophyllite or Bronzite? we promised to cover it next or now.

Credit for finding and then quickly realizing that an assortment of dark crystals in a chunk of mica schist probably wasn't the expected schorl goes to Bob Simonoff of Middletown, Maryland. He is shown at left with his 12 year old daughter Jessica, a mineralogical prodigy whose knowledge and accomplishments have brought international reknown. Having nurtured Jessica's interest enough to acquire the "mineral bug," Bob set out on his own one day early last March for a relaxing day in the field, first at Carroll County's Springfield dumps, later Rockland in Baltimore County.

He had been to Rockland last fall with Jessica. Near the trail extending from the parking lot above where Falls Road crosses Jones Falls, they had found plenty of notably small schorl crystals in mica schist. Six months later, after the passage of winter had thinned considerable undergrowth, there was more ground to cover.

"I started kicking around and noticed again more mica schist with crystals. At first, I thought they were simply bigger schorl crystals, but they were really shiny and glassy. The first one I picked up had a fair sized crystal on it. I took a look at it and realized: Wait a minute, that's not schorl."

Simonoff's conclusion only became more certain after bringing a piece home to examine the crystals under a scope. Their cross sections were unusually flat for schorl, while fragments revealed the crystals to be be dark brown in colour, rather than black such as schorl. Bob posted magnified pictures on his Facebook page.

"Julian Gray,Curator of the Tellus Museum in Carterdale, Georgia, looked at themand asked for a couple of other pictures. Ultimately he expressed no doubt but that they were staurolite. I had suspected it was staurolite, but this was the first more knowledgeable confirmation that it really was. I'd never encountered gemmy staurolite and was only used to seeing those more typical earthy twins."

Closer to home, however, those in the know refrained from going on record with a visual identification. At first glance, the crystals very much resembled tourmaline; if not schorl, then perhaps dravite, which in this part of the country occurs primarily in marble.

Even John S. White, past Curator-in-Charge of the Department of Mineral Sciences at the Smithsonian's National Museum of Natural History, though believing the crystals to be staurolite, was reluctant to make the call. So he sent a sample for analysis to his friend Dr. Peter Leavens, Professor Emeritus of Geological Sciences at the University of Delaware. Confirmation that the material was indeed staurolite reached him on June 18.

The trail near where Simonoff found the specimens, which years ago replaced the Ma and Pa Railroad is in Robert E. Park. It has long been popular with hikers and joggers, as well as noted for passing a pegmatite dike and later accessing a trail that leads to the Bare Hills serpentine barrens. Neither spot, however, proved to be the site of Bob Simonoff's find. Though dogwalkers continue to be ubiquitous, the park is officially closed and off-limits for collectors.

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