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.

The Great Arizona Diamond Swindle

Ship Rock close to the diamond fields

The guys that dreamed up the Great Arizona Diamond Swindle sure did a good job of it, and one that sucked in some smart money from both coasts.  Its locality was way out in the boonies of New Mexico.  Bluntly it was salted with uncut stones from Africa where vast amounts of diamonds were found in the newly discovered kimberlite deposits.  The so-called rubies that accompanied the diamonds turned out to be garnets that were mistaken for rubies. The swindlers salted so many diamonds of the property that even after the swindle was exposed people were still finding diamond crystals on the site.

This was a well organized swindle based on the idea in many American’s heads that the West was a treasure house of riches waiting to be tapped.  At the time companies were organized to tap these riches, and the locality the swindlers chose in New Mexico was made for a swindle.  At this locality there were not only diamonds, but rubies, emeralds and sapphires too.  This scheme got off the ground in 1870 that was represented in San Francisco by Phillip Arnold and John B. Slack who claimed to have found precious gems in the Territory of New Mexico.  On their part they showed off more then 80,000 carats of rubies and a large quantity of diamonds including one crystal weighing 108 carats.

A large group of investors visited the diggings and collected a large number of gemstones that were literally scooped off the ground, and returned to San Francisco where the gems were put on display so other suckers could be reeled into the scheme. At the time someone remarked it was not expected they could pick them up by the bushel, but there they were.

They even roped in the Federal Government because on May 10, 1872 a bill was passed in Congress in the interests of the diamond miner who had made the discovery.

A larger expedition was planned that included a mining expert that had graduated from the Royal School of Mines in Freiberg, Germany.  This expedition was expected to last for sixty days.  This expedition left Rawlings, Wyoming on May 28, 1873 going southwest to the gem mines, but after a while they claimed they had lost their way and proceeded northwest for several days.  Some of the party began to doubt the truth od the scheme, but finally after a circuitous route then finally arrived at the site, and the mountain promised to be a real Golconda.  Everybody found gems, and gems aplenty with their hope rising accordingly.

A third party set out late in the season to return to this fabulous locality, but never got there, and this expedition was abandoned.  When Clarence King the head of the United States Geological Survey heard this third expedition had come to naught he organized an expedition of his own.  It was King’s expedition that proved the whole scheme was a Humbug and brought the whole scheme crashing down around the ears of the plotters. It's estimated this pack of crooks got around $750,000 in 1870s dollars.

The Diamonds of the Wyoming Craton

Bedrock map of North America   USGS

This is a tale about how riches were overlooked in Colorado, Montana and Wyoming by gold seekers in days of yore.  In these three states a whole diamond province has been overlooked in the kimberlites by the hundreds that underlie these states.  The diamonds can also be found in lamproites, lamprophyres and other cryptovolcanic structures that are associated by the Wyoming Craton underlying these three states.  Many of the larger targets lie right next to I-80 between Cheyenne and Laramie that remain unexplored.  This area was originally discovered by early gold miners who discovered it contained little or no gold so they passed it on.

Subsequent discoveries indicate this may be one of the most unexplored diamond provinces in North America where the diamonds can be found in the carbonate rich sediments found in a Archean gneiss.  More then fifty depressions have been discovered here suggesting cryptovolcanic activity that lie east of the State Line diamond district.  It is thought these depressions could be kimberlites containing possibly large amounts of diamonds. 

Ongoing exploration suggests that the Wyoming Craton contains a world-class diamond province and like the diamond province near Marathon, Ontario also contains large deposits of colored gemstones as rubies and sapphires.  This craton is found covering a large portion of Canada.

The Wyoming Craton aside from covering several western states also includes exposures in Alberta and Saskatchewan. Diamonds have been discovered in both the kimberlites and lamprophyres in Montana, Wyoming, Colorado, Kansas and Nebraska as well as Canada.

Another potential place where you can look is in any conglomerates that are derived from the lamprophyres and kimberlites of the Wyoming Craton.  One of my prospecting buddies has found a diamond deposit like this near Marathon, Ontario.  Another Canadian prospecting buddy that lives in western Ontario has also found probable diamonds in his part of the province.

It isn’t just diamonds that can be found there; recently one of the world’s largest deposits of rare earth metals was found in Nebraska,  When you start poking around in this ancient craton you never know what you’re likely to find.

The Wyoming Craton has the greatest southwestern outcrops of Archean rocks in North America.  Theoretically terranes like this have deep roots in the lithosphere that according to Clifford’s rule this deep keel is necessary for the formation of kimberlites with their association with diamonds.  Although this terrane wasn’t deformed during the

Ancestral Rockies Orogeny it was pervasively deformed during the Laramide Orogeny and one theory has it that its deep keel was removed partially or wholly allowing it to be deformed during the Cretaceous or later.  

Finding Diamonds in California

Uncut diamonds

From the earliest days of the California Gold Rush diamonds were found in the tailraces of sluice boxes that were used for gold washing.  Diamonds were found not only in recent stream gravels but much older gravel that was buried under layers of lave and tuff from ancient volcanic activity as fossilized stream channels that ran along the mountains from north to south.  These stream channels indicated an ancient stream flow that was almost at right angles to the present day flow.

The biggest problem with California diamonds is there just are not enough to make going after them profitable. Most of the stones have been found as a result of gold washing operations in both present day streams and in the fossilized beds of earlier streams. Many of the diamonds were destroyed by the use of stamp mills used the breakup the gold ore retrieved from the fossilized streambeds. Their presence was noted as fragments seen in the gold ore. The diamonds that were recovered from ore were for the most part small or industrial grade diamonds.

As early as 1853 diamonds were discovered on top of Table Mtn. about thirteen miles north of Oroville on state Highway 70 close to the ghost town of Cherokee.  It was in the gold diggings surrounding the town that reportedly more then 300 diamonds were found most of them being of industrial grade.  Claims have been made that at the time this was the largest discovery of diamonds made in North America.  This has been exceeded with the discovery of several diamond producing areas in Canada.

Cherokee was the site of the only diamond mine in California, and it was here the first diamonds were found.  Mike Maher discovered a perfect blue diamond when he was cleaning out his sluice box in 1866.  Other diamonds were found here with one of them weighing six carets, but because gold was the primary concern it is unknown how many millions of dollars worth were discarded with the mine tailings produced by the hydraulicing for gold with high pressure jets of water that washed away the gold ore.  

The fact that diamonds do occur in California is well attested to in newspapers and scientific journals.  In some cases however it is readily apparent that many of these so-called diamonds were in fact quartz crystals that had become rounded because of stream action.  One such quartz crystal had been used as a marker in a game of marbles where it show several percussion marks that were the result of being hit by marbles.  A diamond would not show such percussion marks, but would rather cleave into pieces instead waiting to be found in the sluice boxes at work in the area.

The Georgia Marvel and other would be gemstones

A large crystal of sapphire from Madagascar
Photo by Rob Lavinsky 

This was found in a stream in the Blue Ridge Mountains of Georgia in 1883 and was purported to be a sapphire worth $50,000 by its finder who was assured of its authenticity by two different southern jewelers.  This fabulous find was also known as the Blue Ridge Sapphire.  The jewelers had arrived at a value for the stone based on its weight of several carats.  Eventually this stone was proved to be a hunk of rolled blue-bottle glass that took coating it onto some platinum wire to convince its finder.

This is a glaring example of how little the average person knows about gems and it seems that fallacy more then truth is known by the general public.  One of these fallacies is the belief that any stone that can be scratched by a file has to be glass.  Another is that is when a stone is hit with a hammer it’s a fake.  These practices have led to the destruction of many valuable gems.

The United States has an abundance of all types of gemstones that has never been appreciated by the average person.  In many cases these gems have been produced as a byproduct of other mining operations where many of them have slipped through the operation to be lost.  Many of the stones that were saved were discovered in places where gold was being washed with the miners being attracted to a gem because it was a shiny pebble.

Gold washing was not limited to the western US, but was also practiced in the South starting in the early 1800 with the discovery of gold in North Carolina.  It is difficult today to appreciate the size and scope of these southern gold deposits that ran through the Piedmont and Blue Ridge Mountains.  In many cases the stream banks for miles were covered with mine tailings. 

The gold wasn’t limited to placer deposits, but many mines were also producing lode gold.  Many of these mines were destroyed during the Civil War.  Recently the Haile Mine in South Carolina was found to have reserves of gold exceeding 3,000,000 ounces.  A Canadian mining company is in the process of reopening this mine.

Another of these wonders was a stone weighing more then nine ounces that was discovered near Gibsonville, North Carolina that was deemed to be a real emerald by some local expert by some “local expert.”  A microscopic examination of this stone contained numerous small sparkles of light that were thought to be tiny diamond crystals.  This stone was eventually proved to be a quartz crystal having long hail-like crystals of hessonite and actinolite that also had a series of small bubbles in a stream-like pattern filled with liquid that sparkled in the light like diamonds.

In truth the United States has produced virtually all the precious and semi-precious stones in the world.  For the most part these stones remain in the ground through lack of interest of outright ignorance.  There is also a prevalent belief that gems come from some far-off romantic place that it is difficult to reach from here.   

The easy way of Identifying your gemstones and minerals

Semi precious gemstones
Photo by Mauro Cateb

All gemstones are minerals, but not all minerals are gemstones, so the limited knowledge imparted here can be used on both gemstones and minerals.  If you can’t tell what kind of gems you own don’t feel bad because there have been plenty of emperors and kings that didn’t have a clue about what kind of stones they had in their own crown.  A good example of this is the Black Prince’s Ruby that resided in the Crown of England for hundreds of years before somebody found out it was really a mineral called “spinel.”  This is a stone that looks like a ruby but is a much less expensive stone then real ruby.  Clear white topaz is often mistaken for diamond and in the past many large diamonds have been found to be really topaz.  Identifying these stones is in the realm of the gemologist who is specially trained to identify gemstones.

A translucent ruby
Photo by Rob Lavinsky

There are several stones that are treated as gemstones, but aren’t.  Amber is a glaring example of this, a stone that is treated as a gem but in reality is fossilized tree sap having many inclusions of insects and other organic matter.  Petrified wood is another example that is often beautiful and is treated by many as a gemstone, but isn’t.  Jet, the black stone is actually a variety of coal and far from the definition of a gemstone, as are pearls.  Pearls have the distinction of being the most valuable stone, but they aren’t gemstones either.

Identifying gemstones and minerals is really a process of the elimination, for instance if you are presented with a green clear gemstone it is not apt to a ruby. More than likely it is emerald, but you really can't be sure without further tests. There is a variety of garnet called demantoid that is also green and is often mistaken for an emerald. One of the most important tests that are used in mineral identification is the color of the stone.

Hardness is another criterion that is used. This is based on the Moh’s hardness scale that ranges from 1 to 10 with diamond being the hardest and soapstone the softest. Most stones that are used in making jewelry are harder than seven on the Moh’s scale even though some stones that are as soft as three on the Moh’s scale are faceted for collectors. You can buy hardness testing kits or make your own from various minerals that work’s as good as store bought.

Turquoise from Mojave County, California
Photo by Rob Lavinsky

The looks of the stone are important is it transparent, translucent or opaque.  Transparent means can you see through the stone so things can be seen clearly that are behind the stone.  Translucent means does light pass through the stone, but you can’t make out objects that are in back of the stone.  Opaque means light doesn’t pass through the stone, and you can’t see through it.

Streak is literally a thin mark of the mineral or gemstone composed of very fine powder left on a piece of unglazed porcelain colored either black or white.  Black is often used to test for gold and other precious metals when it is known as a “Touchstone.”  It is often used in conjunction with acid to see if there is a reaction between the streak and the acid.  The karat weight of gold can be determined by treating its streak with various concentrations of nitric acid.

2x2 inch black and white streak plates,  White is pyrite and black is rhodochrosite

We sell streak plates: Click Here 

Cleavage and fracture are other important tests.  Fracture is most important for quartz gemstones that break in a Concoidal fracture that looks like little clam shells.  Some minerals like jade have a hackly fracture i.e. a rough appearance.  Some stones have a pronounced cleavage like topaz or diamond.  Topaz is especially prone to a perfect basal . cleavage causing it to be a poor gemstone.

Specific Gravity was discovered by Archimedes when he was tasked to find out if a gold smith cheated the Tyrant of Syracuse when he was making a golden crown for the tyrant.  This was a job that required quite a lot of forelock tugging on the part of Archimedes until he finally threw his hands up and decided to take a hot bath. His slave girl filled the bathtub to full of hot water so on Archimedes claimed into the tub it overflowed. He had discovered the principle of specific gravity, and with that he jumped out of the bathtub and went streaking through the town agora of Syracuse yelling at the passersby Eureka, Eureka that means I have found it, I have found it. They all thought he had gone nuts, and if it wasn't for the fact his brother-in-law was the tyrant he will probably been slapped in jail.

What Archimedes discovered was the body would displace an equal amount of water according to its volume, or in modern terms its weight per cubic centimeter. This is normally taken by first weighing the object in air and then weighing in water. The difference is its Specific Gravity.

These are some simple tests that can help with gemstone or mineral identification there are others that are far more complicated that can be used in conjunction with the simple tests. Although there are over 2000 recognized minerals in the world there are only about 300 that are common rock forming minerals that you are apt to encounter in the field. A good source of information about most minerals can be found at www.mindat.org. 

What Diamond Crystals look Like

Interpenetrating cubes of diamond
Photo by Rob Lavinsky

The word morphology means what it looks like.  Diamond crystals are a good example of this as in the growth process they are able to take on many guises.  They all however are caused by the basic shape of the carbon cell that controls the diamond growth.  The carbon cell is used to build the diamond crystal or stated in another way a diamond molecule.  These carbon cells are deposited onto the nucleus of the diamond one layer at a time until the diamond finishes growing.  In its purest form a diamond crystal is cubic like a crystal of sugar.  The addition of various elements however causes a diamond to morph into different shapes or colors.

The most common of these shapes are the cubic form that is square like a salt crystal or the octahedron which is two pyramids stuck together base to base.  From this simple crystal form the shape of a diamond becomes more complex.  This is caused by many different physical process; the most common being the physical space allotted to the diamond crystal to grow.  If this allotted space is cramped and not shaped like a typical space the diamond crystal will grow into the shape of the space.   Something that will further complicate the final shape of the diamond crystal that is delivered to the surface of the Earth is the dissolution of the diamond in carbonate or silicate bearing water at the pressure-temperature conditions encountered in the diamond stability field.  This was established experimentally by Alexander F. Khokhryakov and Yuri N. Pal.Yanov of the Siberian Branch of the Russian Academy of Science in Novosibirsk Russia. 

The macle another form of diamond crystal
Photo by Rob Lavinsky

One of the stranger forms of diamond growth is exemplified by the rough diamonds from the Ekati, Diavik and Snap Lake mines in Canada.  These diamonds are dug out of the ground wearing fur coats that are fibrous overgrowths of diamond crystals with a transparent diamond crystal at the center.  Apparently somebody told these diamonds they were coming from Canada, so they came prepared for the Canadian weather.  How this came about was the diamond crystal had more then one stage of growth. 

There are one or more generations of crystal growth in most diamond crystals.  A diamond crystal can also undergo retrograde growth where conditions either in the area in the mantle where it was formed or on its way to the surface in kimberlite magma.  Some of these crystals can become bizarre in their appearance, and some of the more bizarre are what are called skeletal crystals.  Sometimes the diamonds are etched into more rounded shapes by the action of the chemistry of where they are formed or transported.

The macle is another shape the diamond can naturally take this is a twinned diamond taking a triangular shape and has two large triangular sides.

References:

Harlow, George E., The Nature of Diamonds, American Museum of Natural History, © 1995