Mining Gems in New England
Did you know that New England contains some of the most important gemstone deposits in the world? Every state in New England produces gemstones in commercial quantities of one type or another. It is possible to make a living out of New England's gems and some people do. This is evidenced by the number of rock and mineral shops there scattered all over New England. Some of them are part time operations yet others are operated full-time. Many others just operate at gem shows, or over the Internet. All of these shops have one thing in common the close proximity to local gem deposits.
Many of these gems are found in a special kind of rock called a pegmatite. A pegmatite chemically is the same as granite. It forms as a tabular intrusion into other rocks, and by cooling much slower then granite it has giant crystals. The largest single crystal ever found is in a pegamite in the Ural Mountains in Russia
Among the pegmatites the ones that are termed "dirty" containing lithium minerals are most likely to produce gems. The most common is beryl that makes a series of gems starting with the emerald, aquamarine, heliodor and many other colors. Another gem associated with pegmatites is topaz. Even large garnets are seen in pegmatites.
In New England one finds a belt of pegmatites that reaches all the way from western Maine across New England to the eastern side of the Connecticut River all the way to Long Island Sound. This is called the "Bronson Hill Anticlinorium." Throughout the length of this geological feature that covers hundreds of miles one can find gems associated with the pegmatites.
Another source of gems are the trap ridges found along the lower Connecticut River, and in Maine where the most common gem material is Amethyst, and minerals of the Zeolite family. Some of the amethysts found in rocks of the same era along the west side of the Bay of Fundy are in the crown jewels of France.
Much of New England is covered by metamorphic rocks. Here is another rich terrain to collect gems. The most abundant gem associated with these rocks is the garnet. Others are those called anhydrous aluminum silicate. These can take several forms; staurolite- chiastolite, kyanite and sillimanite. Staurolite crystals twin into a cross shaped stone called chiastolite or fairy crosses. Kyanite can be cut into a beautiful blue gem. Sillimanite is also known as fibrolite in this form it is a highly attractive gem.