Saturday, November 28, 2009

Uncovering a Spectacular Maryland Specimen

The above pictured spessartite garnet atop schorl tourmaline is one of two Maryland specimens displayed in the University of Delaware Mineralogical Museum. As I photographed it, the Museum's curator, Dr. Sharon Fitzgerald, informed me that her husband, Dr. Peter Leavens, had dislodged it from a road cut near Elkton. How on earth did he do it, I wondered, and exactly where?

Dr. Leavens is currently Emeritus (retired) Professor of Geology at the University of Delaware, where he taught for 38 years. He was also Curator of the Mineralogical Museum from 1972 to 1997, and is married to the museum's present curator, Dr. Fitzgerald. At her bidding Dr. Leavens wrote up for me what happened. Here is his story:

On the official Maryland state highway map, Appleton is marked as the most northeasterly town site in the state, although there is nothing there except a convenience store at the crossroads where Appleton Road, connecting Elkton, MD and Kemblesville PA, crosses MD 273.

In the mid 1970s I was teaching at the University of Delaware and living in Kemblesville. My commute took me down Appleton Road and into Delaware on 273. One day in late summer I saw that a development road (now North Edgewood Drive) was being built off Appleton Road to the east, a few hundred yards north of the crossroads.

Scouting along the road, I found some large quartz boulders which had been plowed out of the roadbed and piled on the bank. The road had cut across a pegmatite, about four feet wide and at least as long as the road width. Judging from the limited outcrop exposed in the road, the pegmatite had an outer quartz-feldspar zone and a discontinuous quartz core; the boulders on the bank were pieces of the core. What got my attention were the crisp outlines of several black schorl tourmaline and tan microcline crystals embedded in the margins of the quartz core boulders.

I had my sledge hammer in the car, so I got it out and began beating on the quartz boulders, hoping to jar the crystals loose, and I was able to recover several tourmaline crystals and part of a microcline crystal. By far the best specimen is a 2.5" tall schorl capped by two 1" garnet crystals. One garnet, which had not been protected by the quartz, had crumbled almost completely away, but the other is a crisp trapezohedron. One corner of the tourmaline came out in several fragments and had to be repaired, but overall it is a beautiful specimen.

The bedrock geologic map of northern Delaware shows that the northwest corner of New Castle County, including part of Newark, contains abundant pegmatites. During the building of West Branch development in Newark in the 1990’s, a number of pegmatites were unearthed that produced schorl tourmaline, a few beryl crystals, and some small garnets. The Appleton occurrence is only about three miles west of West Branch and may be part of the same pegmatite swarm.

If so there may be other finds to be made in the northeast corner of Maryland. Unfortunately, both the Appleton and the West Branch pegmatites are covered, and no traces of them remain.

Contributed by

Dr. Peter Leavens

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