Tuesday, December 4, 2012
Colored Crystal's Continued...
The most famous Wulfenites from Red Cloud mine in Arizona have an incredible intense red color. Research has shown that chromium, valence 6, is transfer charged electrons back and forth with oxygen, valence 2, to cause the color. The bright red-orange color of Wulfenite found in the San Francisco mine Sonora, Mexico, have not been tested but it would be a reasonable assumption that they contain the same two stunning minerals.
One interesting form of quartz is rose quartz. It is a Charge Transfer Mineral, but it's color can hardly be considered rich. One study has shown that the pink of rose quartz can be due to pink clay, probably montmorillonite clay, diffused in the material.
One of the gems that can take on a panoply of colors is sapphire. One reason sapphires are highly regarded is their intense color, which is often due to some sort of transfer action. Sapphire has the same chemical makeup as ruby; both these corundum gems starts out as a colorless aluminum oxide. Ruby's color is caused by the transition metal element chromium, valence 3. Sapphire on the other hand is a Charge Transfer Mineral that can play host to any one of several trace elements.
Rich violet sapphire may have the most complicated cause of color. This Charge Transfer Mineral requires traces of iron, valence 3, and titanium, valence 4, to shift electrons to divalent oxygen, but this action can only take place when chromium, valence 3, is present.
Blue sapphire is very much like violet sapphire, as the iron-oxygen-titanium transfer takes place to form the color; but in this case iron, valence 3 and iron, valence 2, are participating.
Yellow Sapphire is a bit simpler, as oxygen, valence 2, shifts electrons with iron, valence 3. Keep in mind that all this electron transfer business going on requires energy.The light that enters a sapphire crystal supplies that energy by giving up a part of its color spectrum, depending on which trace elements are present and functioning!
The most desired of sapphires is the orange-pink variety called padparadscha a Sinhalese word for "lotus blossom". Unlike all the other sapphires, this orange-pink gem only needs chromium, valence 3, to function as a color center. It can also gain color when chromium, valence 3, works with magnesium, valence 2, to replace two aluminum, valence 3, atoms. This one is not Charge Transfer, but simply substitution, and the color is stable.
Winks 12 Days of Christmas at HPDiamonds
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Wednesday, November 28, 2012
Now that's a Stone of a Different Color!
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.

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".
Wednesday, November 14, 2012
U.S. Retailers Go Green

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.
Wednesday, November 7, 2012
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.

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:

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:

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.

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.
Thursday, November 1, 2012
CVD ALERT!
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The important thing here is to get informed. The National Gems and