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Volume 2 Issue 7

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Gold, Silver, Aquamarine, and Maybe Even Diamonds

By Vincent Valade

I did my first mineral collecting in Goffstown at the age of nine.  My parents were having an artisan well drilled for their new home when the drill bit encountered a quartz crystal seam at about the 150 foot level.  Quartz crystals coated with a light iron stain to almost a half inch long were washed up to the surface.  I spent many hours raking through the washed up stone dust piles for the sharp little points.  I would later find that these quartz crystals were evidence that my parents house sits on an old fault.  

There are several siliceous faults that run northeast to southwest in the southern end of the state.  Two of these touch parts of Goffstown and are both named for hills in Hooksett.  The Campbell Hill Fault starts in Rochester, continues southwest through several towns including Northwood and Manchester, before exiting the state in Mason.  This fault just nicks the southeast corner of Goffstown.  The Pinnacle Fault runs parallel to the Campbell Hill Fault and starts in Epsom running almost along Rt. 28 into Hooksett, Bow, and Dunbarton, before entering the northern part of Goffstown.  

Since the quartz that was deposited along these faults during formation is much harder than the surrounding bedrock, erosion has left many solid quartz hills and ledges behind to mark these faults.  Some of these have produced good quartz crystal specimens.  Flint Hill in Raymond, Campbell Hill in Hooksett, Quimby Mountain at the Hooksett - Dunbarton town line, and Rattlesnake Ledge in Goffstown are some of the better locations to collect.  Although most crystals seldom exceed a half inch in length, many examples approaching two inches in length have been found.  

Rattlesnake Ledge is about two and a half miles north of Grasmere village.  The other ledge with quartz crystals in abundance in Goffstown is Purgatory Pond Ledge.  Much larger crystals are found just over the Goffstown border in Dunbarton at Quimby Mt.  On the southern side of the peak at Quimby Mt. is a large open pocket of weathered quartz crystals about a half meter in diameter.  All of these hills have bare rock tops polished smooth by the glaciers.  If you look carefully, you will notice scratches made by rocks trapped at the glacier bottom.  These scratches give an exact direction of the movement they made.  

If you've read "New Hampshire Mines and Mineral Localities," by Philip Morrill, you might have noticed the reference to an old silver mine just north of Snook Road.  When looking for this old mine in the seventies, I was directed to small hole by a boulder.  The locals, who had pointed out the mine had no idea I was looking for something slightly larger than a two meter by one meter deep hole in the ground.  

The hill directly behind the mine is called Mineral Hill, which also contained the same schistly rock that was in the mine hole.  Although none was to be seen, I could only assume that like the rest of New Hampshire, the source of silver was in some galena.  Some of the state's galena has assayed out to as much as 26% silver.  Enough silver was obtained to produce two small rings.  

Although I've looked several times for it and couldn't find it, there is a gold mine on the southern side of the Uncanoonuc Mts.  A few years ago a couple of hunters, who couldn't pin down the exact location, reported it to now be a bear den!

Along the banks of the Piscatoquog River, below Goffstown Village, is the state's only known occurrence of the rock Kimberlite.  This rock has been the source type rock for many diamond mines.  Although finding Goffstown's material to be diamond bearing has poorer odds that winning the lottery, it's still nice to daydream.

 "Big Deal," you say.  "Two little silver rings, a lost gold mine, a Kimberlite outcrop and some quartz crystals.  What does Goffstown have to really excite me?"   In one word - Aquamarine!

At the turn of the century Mr. Brown had a large farm, now called the Peaceful Valley Farm at Brown's Corner on the southern side of the Uncanoonuc Mts.  On occasion he would travel up the mountains to find pegmatite outcrops to drill and blast with black powder.  Several fine gem aquamarine crystals were found.  I first remember seeing two of them at Harvard University's Peabody Museum in the early seventies.  Although less than two inches long and half an inch in diameter, they are solid gem aquamarine.

Pegmatite outcrops have been found in about a two mile wide area from the Uncanoonuc Mts. to Glenn Lake.  During the construction of Glen Lake Dam, some aqua was found.  Also, in the mid 1990's, Worthley Hill produced some gem aquamarine.  A couple of 4.5 carat stones were cut.  The stones cut were light in color but very brilliant.

Associated minerals at these pegmatite outcrops included grossular garnets up to two inches in diameter.  Schorl, biotite, muscovite, microcline, and solid masses up to two inches of arsenopyrite are present.  There's a story that in the forties of fifties, a doctor in the Manchester area purchased a solid gem ten inch long crystal.  But with the trail cold for over fifty years, nobody knows where this crystal is now.  Many areas remain to be prospected around the Uncanoonucs.  Make sure to mind any "No Trespassing" signs, and asking permission to dig if you find a pegmatite, since almost all the land in town is privately owned.

Acknowledgements:

The author would like to thank Robert Whitmore for his guidance and use of his extensive library.  Also, William Metropolis for verifying arsenopyrite as the sulfide present in the Uncanoonuc pegmatities and my daughter, Jennifer for her grammar corrections.

Bibliography:

Hadley, George P. (1922). History of the Town of Goffstown, Vol. I. Concord: Rumford Press

Hitchcock, Charles H. (1877). Geology of New Hampshire, Vol. II. Concord: Edwarda, Jenks, State    Printer.

Lyons, John; Bothner, Wallace; Moench, Robert; Thompson, James. (1997). Bedrock Geologic Map of New Hampshire.  Colorado: U.S. Geological Survey.

Meyers, T. R. (1941). NH Mineral Resource Survey, Part VI, Some NH Quartz Deposits. Concord: State of New Hampshire.

Morril, Philip. (1960). New Hampshire Mines and Minerals Localities. Hanover: Montshire Museum.

(1961). Goffstown, New Hampshire, Bi-Centennial. Goffstown.