Gemstone Occurrences in Massachusetts

This is rhodonite of the type found in the Betts Mine it is also the state gem of Massachusetts
Photo by Phillipe Giabbanelli

Massachusetts is another state that is sparsely supplied with gemstones although there are some exceptions one of which is the Betts Mine in West Cummington that produced some very fine rhodonite for years.  The rhodonite accompanied by rhodochrosite is respectively manganese silicate and carbonate both are cut as gems.  Rhodonite is also the state gem of Massachusetts. 

Rhodonite was first discovered as float from the glacier during the 19^th century where the American Gem Company part of Tiffany & Co., became aware of the float.  They used the rhodonite for making knife and umbrella handles as well as dinnerware.  There is a place setting on display in the American Museum of Natural History in New York City made from rhodonite from Massachusetts.  The deposit that is at the contact between the Hawley and Savoy schists was developed by Anson Betts who mined the rhodonite for use as flux on welding rods and later mined it as a gemstone.  The mine was bulldozed shut after the death of Anson Betts and is now closed to collecting.  Rhodonite is still available from the site in the form of mine tailings where it is still collected.

Down the road from the rhodonite deposit to the east is the small village of Lithia in the town of Goshen where the mineral called spodumene was mined in the late 1800s.  This is an area of LCT pegmatites where the first colored tourmaline was discovered in a quarry in the town of Chesterfield in the early 1800s.  Goshen is the Dana type locality for the variety of beryl termed “Goshenite.” a colorless variety of beryl.  The same pegmatites also produce blue tourmaline, petalite and pollucite a cesium aluminum silicate mineral. Beryl has also been found in a pegmatite at Royalston in Worcester  County.

This is margarite a rare form of mica on emery from the mines at Chester, MA.  Emery is the black mineral that the margarite is hosted upon.  Margarite is a brittle form of aluminum rich mica associated with emery deposits.
Photo by Rob Lavinsky

The Chester Abrasives Co. in Chester used to produce emery from the mines west of Chester in about the area where the power lines cross US RT. 20 in a series of mines running north to south for a total of five mines.  In the historical society of Chester there are four apothecary jars containing several pounds of ruby and sapphire crystals that were actually mined in the Cowee Valley corundum mines in Franklin NC operated by the Chester Abrasive Co. in the late 1900s.  Although not mined in Chester they are at least worth a good look.  There is an exposure of gem grade serpentine on the Middlefield Rd. on the right just as you are climbing out of the Westfield River Valley.

The Connecticut Valley offers a completely different suite of gemstones.  The first place to look is in the gravels of the lower Deerfield River because it contains agates that have washed from the nearby trap ridges.  The trap ridges themselves offer good deposits of amethyst and zeolites.  Lanes Quarry in Westfield is the Dana Locality for datolite, however Lanes Quarry is closed to collectors as it is an active quarry.

Datolite from Lanes Quarry in Westfield
Photo by Rob Lavinsky

Garnets are found throughout the state wherever there are crystalline rocks although many of them are rotated making them useless as gemstones.  Most of them are almandine garnets although in the Betts Mine that contains the manganese minerals rhodonite and rhodochrosite there are a rare variety of orange colored garnets called spessartine that are gemmy and suitable for faceting.  Many of these garnets tend to be small, but there are some exceptions weighing several carets.

Spessartine garnets of the type found at the Betts Mine in Plainfield MA where they occur with quartz.
Photo by Rob Lavinsky

A good source about rocks and gems in the state can be found at the many gem and mineral stores dotting the landscape.  Most of these stores stock guidebooks that give specific localities for collection, and many of them are up-to-date,

Finding Gemstones and Minerals in a Pegmatite

The inside of a pegmatite mine, Ruggles Mine in New Hampshire
Photo by Squelle

Pegmatites are mined not so much for their exotic minerals, but the more mundane feldspar, mica and quartz. The exotic minerals that include gemstones are usually a byproduct of this mining. This is true of most pegmatite mines except for a few like the Maryall mine in Connecticut, and the Himalaya mine in San Diego County California. Because pegmatite it is a very hard rock it is almost impossible to mine without the use of blasting is for this reason the average rockhound is usually excluded. However, from prior mining activities it is possible to go over the mine tailings looking for specimens.

Most miners are more interested in the three primary minerals of feldspar, mica and quartz than they are in the more exotic minerals; therefore these minerals are often thrown onto the waste pile where they remain for the rockhounds to collect later. It is among these tailings where most of the gemstones are found.

By working tailing heaps you are working with stone that has already been mined, and broken up making for much easier collecting. Most of the time you'll encounter stones that are not much more than a foot in diameter, and many of them are usually smaller. You will occasionally encounter a larger stone where it is extremely handy to have in your collection of tools a fairly large sledgehammer weighing more than 8 pounds. Most collecting on a tailings heap can be done with a sledgehammer that weighs 8 pounds, and you can do a considerable amount of damage with an eight pound hammer.

For most collecting in a pegmatite one of the most useless things is a regular geologist’s pick because most of them are too light. What is far more effective is a 4 pound engineer’s hammer and a bullpoint. Bullpoints are a hardened steel rod about three quarters of an inch in diameter having a hexagonal shape about a foot long and coming to a hardened point on one end..

Some of the other things you need in your tool kit for collecting specimens in a pegmatite is a good jeweler's loup is at least 8X magnification on a chain so you can wear around your neck. A stone chisel is another device that should be included. Your kit should also include some old newspapers to wrap your specimens. A small pad and pencil to write down descriptions of the specimens you have found. You should also leave a number on the newspaper holding the specimen so you'll know what it is when you get home.