New Jersey Gemstones

A variety of tumbled gemstones
Scanned by Adrian Pingstone

Amber that has been preserved since the age of dinosaurs is found in several places in New Jersey where there are Cretaceous rocks one of these places in the area around Sayreville although they can be found scattered throughout the Cretaceous rocks and various localities throughout southern New Jersey. Although there are several deposits of Cretaceous aged rocks in the United States Amber is only found with appreciable quantities in New Jersey.

Amethyst is found in the many trap ridges of New Jersey in both the area of the Palisades and in the Ramapo Mountains.  This variety of quartz is usually found in the cavities in the rock. Many other minerals of the zoisite family are also associated with traprock quarries.

In the past there was extensive zinc mining activity in Franklin and Sterling Hill in Ogdensburg that produced large quantities of zinc minerals.  The mine dumps in these areas are one of the most noted areas in the United States that have produced fluorescent minerals.  Some of these minerals are gemstones in their own right notably rhodonite and sphalerite.  In addition Sussex County is also known for producing other minerals including aragonite, corundum, garnet, pyrrhotite, rhodonite, spinel, tourmaline and williamsite.

Bergen County has produced amethyst, natrolite and opal that are found in the county’s trap ridges.

Mercer County has been known to produce albite, calcite, chabazite, datolite, natrolite, stilbite and tourmaline. Calcite, chabazite and datolite are produced from the trap ridges in the county.

In the far southern part of New Jersey can be found quartz crystals that are called by many Cape May diamonds although the source of these stones remains unknown it is thought they are washed down from some underwater formation further upstream in the Delaware River.  They are found on the beaches of Cape May and surrounding communities at the mouth of the river. The same area also produces jasper. 

Corundum has been found in Sussex County associated with the Franklin limestone as almost perfect crystals seen in cavities in the limestone.  These stones are blue, grey and red that in some places are clear enough to be cut into gems. 

Other counties where gemstones can be found include:

Middlesex - marcasite, petrified wood, pyrite

Morris - carnelian, serpentine

Passaic - agate, amethyst, carnelian, chabazite, datolite, heulandite, pectolite, prehnite

Sussex - aragonite, corundum, garnet, pyrrhotite, rhodonite, spinel, tourmaline, williamsite

Union - calcite, chalcedony, prehnite, sphalerlite

Warren - calcite, chalcedony, garnet, molybdenite, prehnite, serpentine, sphalerlite

Most of the collecting sites are located in Northern New Jersey.  Many of these sites are found at old mines or rockcuts.

Gemstone Occurrences in Connecticut

Almandine garnet, Connecticut's state stone.
Photo by Rob Lavinsky

Connecticut is amply endowed with gemstones ranging from andalusite to zircons.  The stones found in Connecticut are found in a variety of terranes although the primary one is pegmatites, but they are also found in the trap ridges of the Connecticut River Valley.  Even more are found as glacial float if you want to use that method of finding gems.

Just in the town where I live, Barkhamsted there are several different verities of gemstones including almandine garnets, beryl, corundum, kyanite, quartz, soapstone, zircon and the usual rock forming minerals.

Connecticut is blessed with many gem bearing pegmatites one series starts in Glastonbury and Crosses the Connecticut River at Middletown and extends almost to the coast of Long Island Sound.  The other belt of pegmatites extends diagonally across the western portion of the state from Hartland to Ridgefield.  Both of these belts contain many of the gemstones found in LCT type pegmatites.  Many of them are Dana localities and one of them, the Maryall Mine is considered to be one of the most important gemstone mines in the United States.  This mine is famous worldwide for its crystals of aquamarine and golden beryl.  It also contains some bright red garnets that can weigh up to several pounds.

Beryl crystals on Feldspar.
Photo by Rob Lavinsky

The trap ridges of the Connecticut River Valley and in Woodbury contain specimens of amethyst, datolite and prehnite that are found in vugs in the trap rock.  Some of these occurrences are also Dana localities. Many of them are also world famous.  Connecticut has over 600 recognized mines that are now abandoned scattered mainly across the western half of the state, but there is still plenty of gems to be found in eastern Connecticut.

Microlite-Elbalite and Lepidolite found in the pegmatites of Connecticut.
Photo by Rob Lavinsky

The beaches in eastern Connecticut are littered with moonstones that have eroded from the granite eastern Connecticut is known for.  Another stop you should make is the Connecticut Mining Museum that is part of the Sloan-Stanley Museum in Kent where many of the minerals found in Connecticut are displayed along with lots of information about the mining industry that used to be found in the state.  According to many authorities modern mining was developed in Connecticut then spread out all over the world.