Now that's a Stone of a Different Color!

Have you ever wondered what gives a colored crystal it's color?  Well I have.  And I have the answer for you, or rather answers, as there are several factors that cause a crystal to change it's color.  Crystals get their colors from energy band gaps, physical phenomena, the structure of the mineral, the shifting of electrons, charge transfer action caused by a transition metal impurity (charge transfer occurs when electrons uses light energy to shift from one type of atom to another) and irradiation or other energy sources have disrupted it's atomic structure creating a "color center".

For this weeks blog we will focus on "Color Center" Crystals.

Color Center minerals have one of two defects.  In one case, they are missing electrons or have electrons out of position.  Both leave an empty spot in the orbital arrangement of the atoms.  In the other, electrons of mineral impurities have replaced some electrons of a normal element in the mineral's chemical composition.






Chem Class Reminder:  Electrons are a form of energy and any additional energy might get them to shift their position, especially if they are out of place to begin with.

In some flourite (calcium flourine cesium), a rare earth element gets into the same structure, resulting in a charge-transfer situation that produces the colors blue and pink.  the problem with color center minerals is that it is unstable.  It's color is easily lost upon exposure to heat, strong light or radiation.

Amethyst is a perfect example of this.  The luscious violet amethyst has an unusual electron configuration:  Iron ions, valence 3, get into the structure of the quartz, coloring it a lovely yellow.  however if yellow or colorless quartz are subjected to enough outside radiation, some of those valence 3 iron atoms will pick up errant silicon or oxygen electrons that have been ripped from their normal position.  Voila!  Just like that we have ourselves a beautiful violet colored crystal.

Not all color center minerals are unstable, some of them keep their color as their impurities are not energy sensitive.  Allowing them to retain their colors despite outside heat or radiation.

It is endlessly fascinating to me how, what appears to be a shiny colored rock goes through all these natural processes to get where it turns into a "stone of a different color".

U.S. Retailers Go Green

At this year's JCK Las Vegas, U/S/ retailers did some window shopping but many of them kept their wallets closed.  Some dealers looked at their well-stocked display cases and opted out of even going.  Why is that?

One retailer, John Nichols, sales manager at Huntington Jewelers in Las Vegas said "We're not ready to spend more money yet.  We're buying from the public, so we're recycling a lot.  That doesn't make our vendors happy, but that's what you have to do in this economy."

Nichols isn't the only one recycling either.  Tara Silderberg, co-owner of The Clay Pot in Brooklyn, New York said "We are implementing a gold recycling program for our customers to scrap old pieces for credit and we are very excited about it."

Wink Jones offers similar programs, the most notable of which is that he will buy back "Crafted by Infinity" Diamonds at 80% of what a customer purchased them for.  That is a stellar deal.  All other Diamonds he has a separate program for which depends greatly on the cut and quality of the Diamond.  He will buy back various other Diamonds for up to 60% of the customers purchase price.  Why the difference, you ask?  Cut has a great deal to do with the quality of a Diamond and Infinity has the highest quality of cut, any other diamond would need to be sent to be re-cut to ensure that it meets Wink's impeccably high standards.  

According to Nichols who said "The show seems bigger and I'm not real big on big shows.  the bigger they are the less I do business.  I can't afford to spend half my day with one vendor-I'm afraid I wont see everything I need to."  It appears that it is too big to shop.  Which has me wondering if American retailers are over the "Ol' Razzle Dazzle".  Are they exchanging big show for practicality, and if so will we see that change should the U.S. economy pick up?"

I for one, am glad to see even the jewelry markets of America begin to go green, recycling old pieces and buying from the public.  I'm sure that our economy will recover in time, and when it does JCK Las Vegas will have swarms of happy retailers at their "over the top" show... but for now bravo retailers, bravo.  If the jewelry market ever slowed entirely down (which I highly doubt) perhaps you can all go into business giving lessons on financial planning and ingenuity to government run institutions.

The Skinny on Synthetics

Last week I wrote about synthetic diamonds being discovered in Melee parcels.  I'm sure that was a bit of a scare for a lot of folks.  This week I want to give you the skinny on synthetics.

The first thing you should know is that there are two methods for growing synthetic stones.  The first is High Pressure-High Temperature(HPHT), the second is Chemical Vapor Deposition (CVD).  According to Thomas M. Moses, Senior VP of GIA's Laboratory and Research Department, the processes used are both costly and challenging but produce gem quality stones.  However the diamonds produced vary greatly in characteristics.

HPHT:
Moses explains that HPHT was originally introduced by General Electric (GE) in 1954 and mimics the intense heat and pressure that crystallizes carbon into natural diamonds.  These kinds of stones are made in a press that is capable of generating these extreme conditions.  Today there are a variety of these apparatus all with a growth chamber where HPHT diamonds are grown from carbon molecules in a metallic solvent catalyst that is usually made of iron or nickle or a mixture of the two.

The growth time for these stones is on average one week, not too long but the growth chamber is very small, so only a few may be grown at a time.  Because of this draw back most HPHT stones are .50 carats.  Moses says that while this method has been around for over half a century now, it is only recently establishing profitability.  

THE CHARACTERISTIC OF HPHT:
Diamonds are scientifically classified by type based on the amount and location of the impurities they contain.  Almost all HPHT stones are type Ib, with up to 0.5% nitrogen dispersed throughout the stone.  Because the nitrogen is dispersed, almost all of these stones have an identifiable color.  The majority of HPHT stones are in the color grades H-P, the trace of nitrogen atoms is responsible for the yellowish brownish tint.  Under the Microscope, HPHT stones are inherently shaped differently than natural ones.  The HPHT method typically grows cube-octahedral like crystals.  Also, because they are grown in metallic solvents, some stones have metal inclusions.

CVD:
The CVD method differs greatly from HPHT in that "synthetic diamonds are produced by using microwaves or other sources of energy to break down hydrocarbon gas, such as methane, inside a vacuum chamber.  This causes carbon atoms to accumulate in thin layers on a flat diamond substrate-similar to the way snowflakes accumulate in a snowfall," explains Moses.  

This process is a slow one, only .10 mm of diamond can be grown per hour.  This method for growth also has it's limits in depth.  CVD stones over 3mm in depth are extremely difficult to grow.

The CVD method was first successfully tried by Huston, Texas-based chemical manufacturer Union Carbide Cooperation in the 1950's.  It is less costly and challenging than HPHT, but like the HPHT method it has only recently become economically viable.

THE CHARACTERISTICS OFCVD:
Due to their unique growth process, CVD stones are type IIa, which contains negligible amounts of nitrogen and high thermal conductivity.  This method produces flat tubular synthetic diamond crystals.  Because of the gasses used these stones are also brownish in tint.

SYNTHETIC TREATMENT:
Because of the synthetics and their inherent color, manufacturers have begun treating the stones, post-growth, to transform the unattractive brownish yellowish tints into vivid colors.  Through these processes most natural stones can also be altered to a desired color.

Companies like Suncrest Diamonds, based in Orem, Utah use HPHT processing for just this purpose.  Due to ongoing advances in the HPHT process, stones can not only be transformed into an array of colors, but also improved as white diamonds.

Not to worry here, the differences in Natural stones and Synthetic ones are well known and documented.  For a gem lab they are easy differentiators, to the naked eye of man, not so much.  I for one have no doubt that technology will continue to increase and the demand for "better than natural" looking synthetics will increase with it.  
            

CVD ALERT!

Synthetic alerts were first sounded in mid February, when the Shenzhen lab of the National Gem Testing Center (in China) received a parcel of 18 stones weighing 9.5 carats for certification. 

Diamond Lab Equipment

After DiamondSure and Diamond View exam-inations raised suspicions, NGTC used additional laboratory equipment to confirm all the stones as chemical vapor deposition (CVD) synthetic diamonds.  The parcel of stones was purchased from Hong Kong as a natural diamonds, without full disclosure to the wholesale buyer.

Shanghai Diamond Exchange

In April, another two CVD synthetic stones were detected by the Beijing lab of NGTC, and then two more batches between April and August.  In late May the Shanghai Diamond Exchange issued a statement with NGTC encouraging buyers to be cautious, and to disclose information properly.  As the second largest diamond market in the world, China’s trade members are concerned about these incognito synthetics; along with the risk of purchasing them without full disclosure.

As you can imagine this has caused buyers to be much more cautious with whom they purchase diamonds.  Some are avoiding Melee Diamonds altogether. While some are limiting their buys to only a select few trusted suppliers whom they deal with on a regular basis.

The important thing here is to get informed.  The National Gems and Jewelry Technology Administrative Center of the Ministry of Land and Resources of China held a technology seminar on CVD synthetics on September 2^nd and 3^rd in Beijing.  Sixty-Five of China’s gemologists, scientists, and government people attended this exchange of information.  The Ministry of Land and Resources also intends to work with other government agencies to prevent the undisclosed CVD synthetics from damaging the consumer market and the public’s confidence in it.