Gemstone Occurrences in New Hampshire

Aquamarine crystals (beryl) that are like those found in pegmatite pockets in New Hampshire
Photo by Gery Perant

Amethyst is found throughout New Hampshire with locations listed for practically every county in the state as well as on the Isle of Shoals off the coast from Portsmouth.  It is listed in practically all the granite quarries found throughout the State.  Amethyst is a type of quartz having a purple coloring.  The stone was originally classified as a precious stone and was numbered among the crown jewels of France.

Beryl is the official mineral of New Hampshire that is found in the many pegmatites of western New Hampshire and other granitic rocks across the state where it is found as aquamarine and golden beryl.  On a fieldtrip held in conjunction with the Gilsum Mineral Show the author was also present when emerald crystals were found in biotite schist. These were emeralds that comparable in quality with those found at Crabtree Corners, North Carolina.

Amethyst crystals like those found in New Hampshire.
Photo by Rob Lavinsky

Corundum is a mineral that often occurs in granitic pegmatites as well as pellitic limestones although we were unable to find any site specific localities in New Hampshire it is apt to be found in any silica poor rocks.  There have been reports of rubies having been found in the state.  These reports are from the Moosilauke Lake region where it is found in marble.  Corundum is often associated with kyanite in schists. Other places in the state where corundum has been found include the Belknap Mountains and the area around Wakefield. 

Fluorite is calcium fluoride used primarily as flux in the steel making process that although it is too soft to be used as a regular gem is nonetheless faceted, cut into cabochons and used as a decorative stone under circumstances where it will not be subjected to wear and rough handling.  Fluorite can be found in southwestern New Hampshire around the town of Westmoreland where it was mined at one time for flux.  Today these old mines are a collector’s paradise with beautifully colored fluorite as well as several other minerals.

Since 1985 smoky quartz has been the state gemstone of New Hampshire where it is found throughout the state.  One of the best localities for collecting smoky quartz is located in the national forest just outside Conway where it is found in rotted granite in some aggregate quarries. 

The mineralogy collection at Harvard University contains over 200 specimens of topaz crystals that were collected on South Baldface Mountain in Chatham.  Topaz is a common rock forming mineral that is often mistaken for quartz.

Tourmaline is found in the many pegmatites of New Hampshire, and it was just over the border in Maine where the fabulous find was made at Newry Maine in 1972.  Pegmatites are found in many areas of the state, but are especially prevalent in Carroll and Grafton counties.  There is a feature called the Bronson Hill Anticlinorium that is thought to be the ancient island arc that is associated with the Taconic Orogeny of Western New England.

The best place to get information about gems and gemstones is from one of the many rock shops found throughout New Hampshire.

The King of Stones the Ruby

Rubies are a red colored form of corundum a form of aluminum oxide with the chemical formula of Al₂O₃.  This is the same mineral that produces sapphires that are found in blue and virtually every other color except red that color is reserved for the ruby only.

A ruby crystal on calcite.
Photo by Rob Lavinsky

To be a ruby the mineral corundum has to be colored pink to blood-red where the color is caused by a minute quantity of the element chromium.  The red color gives it its name “ruber” that is the Latin word for red making for an easy move to “ruby” in English.  In the trade ruby is considered one of the four precious stones the others are diamond, emerald and diamond.  Some people consider natural pearls to be the fifth precious stone although the owe their origin to natural processes produced by a living animal.

Hands down a good ruby exceeding 10 carets in weight is the most valuable of all gems.  Like any other gem the prices for rubies are mainly determined by their color, so that the most valuable stones are those that are bright red the so-called pigeon blood-red that commands a huge premium price when compared with any rubies having a similar quality.  The same as grading diamonds the next criteria for rubies is clarity where a clear stone will also command a premium.  However, a ruby containing needle like inclusions of the mineral rutile will often produce a star on a ground specimen that commands a high price as a star ruby.  Most rubies have been heat treated causing the rutile inclusions to vanish indicating that the stone has been treated.  The final quality that can determine a rubies price is cut and its weight in carets.  A recent price quoted for a ten caret pigeon blood-red stone was $24.000 per caret.  This meant the stone had a wholesale value of $240,000.

A cut pigeon blood ruby.

Rubies are most often found in suture zones, a good example is the ruby deposits found in the Mogok Valley of Myanmar where the rubies are found in an altered limestone that when it was laid down received a clay containment that was rich in alumina.  When the limestone was metamorphosed to marble the alumina that is aluminum oxide was converted into corundum.  The addition of a small amount of chromium ions caused the corundum to produce rubies.

Rubies are often a component of marble a good example of this is the occasional ruby crystal found in Franklin, New Jersey.  Sometimes marble undergoes further metamorphism into a rock called amphibolite that also can contain rubies as it does in a newly discovered deposit in southwest Greenland.  Although the stones in this deposit are small they make up for it by being almost perfect pigeon blood-red.

One of the necessary criteria for the formation of all rubies and sapphires it that they form in a rock that is starved of silica;  sometimes these stones are found associated with deposits of ultramafic rocks that is the apparent association where many rubies have been found in the gravel of the Cowee River in Franklin, North Carolina.

This is a place where the general public is invited to find their own rubies by washing, and separating the rubies from gravel.  Most of these stones are heavily contaminated with impurities, but many make some very fine gems.  Occasionally a stone is discovered that rivals the best stones produced in Myanmar.  Rubies are also found in several other parts of the world notably in Madagascar and Sri Lanka where they are found in gem bearing gravel.