What makes a gem, a gem?

A gemstone is a natural mineral that possess a combination of three important properties that will make it “stand out” from just any ordinary mineral that you would find digging in a field. It must be rare: If it’s a very common mineral that anyone can dig up in any field in any country at any time, it stands to reason that it would not be considered a “gemstone”. It must also must possess some degree of beauty: It again stands to reason that no one would hold an ugly mineral in high esteem or that it would hold any value to anyone. People will not buy or hold onto any gem that is unattractive so it would never gain any popularity. Lastly, it must be durable: For any mineral to be considered a gemstone it must be able to withstand fashioning and wearing into jewelry. No one would ever buy or want a lovely rare mineral if it where to dissolve in plain water or crack apart in your fingers. When a mineral is beautiful, rare and durable, it is classified as a gemstone and is usually collected worldwide.

What makes a gem valuable?

It is a combination of a few factors. Firstly, we consider the same conditions that makes a gem, a gem. The rarity, beauty and durability of the gem are extremely important. The rarer, the more beautiful and the more durable it is compared to other gemstones, the more valuable it will be. Also there are two other criteria. The general “availability” of the gem is very important. If a gemstone is so rare that it only appears on the market now and then, it is very difficult for the gem to gather “momentum” and garner up excitement because it just simply is not that available, so people forget about it……..even if it’s very rare! Also, the amount of media attention and advertising a gem receives can greatly influence the market demand and therefore the price. Unlike diamonds, there is no stabilized world price for colored gemstones and they are traded based on supply and demand. It’s all these factors going on at the same time that will ultimately determine how valuable a gem is.

What makes a gem, rare?

A gemstone can be rare for two reasons. First, it can simply be rare because it is almost never found, like the lovely gem Benitoite. It is amazingly beautiful and would take the world by storm if they could ever find more that a few here and there. The few specimens mined keep this gem very valuable. Also, it has to do with how a gem compares with others in its own family, or as we gemologists refer to it as “variety”. A small diamond chip is not valuable at all, almost all diamonds found a around a grain of sand in size, but a 100 carat monster of exceptional color and clarity would make the six o’clock news! Why? Because it is so very rare for a diamond to possess those characteristics, it “stands out” from most other diamonds. The same can be said for any colored gemstone. If it possess a very high clarity and special color and exceptional size, wow, it’s a real find and so it is very rare and very valuable.

What is a "Chemical Composition"?

Remember high school chemistry and physics? Remember the Periodic Table of Elements? That is the table that list all the known “elements” Elements are substances that cannot be chemically broken down any further. Water is H2O, two Hydrogen molecules and one Oxygen molecule “combined together” to make water. If you break down Hydrogen or Oxygen, you just have plain old atoms. All gemstones are a combination of two or more basic elements, that when combined together, form the “chemical composition” of that gemstone. It sounds complicated but it’s not. Remember water? It’s chemical composition is Hydrogen and Oxygen. The only exception is Diamond. Diamonds chemical composition is Carbon and only Carbon making it the only gemstone that is an element and not a “combination” of two or more elements. Ruby and Sapphire have a chemical composition of Aluminum and Oxygen, etc.

What is "Crystal Structure"?

Crystal Structure refers to the orderly and repetitive arrangement of atoms. This definite arrangement directly influences the geometrical form and the optical properties of a gemstone. Gemologists can use crystal systems to help identify unknown gems. For example, all diamonds, spinels and garnets will show similar behavior because they all belong to the Isometric (cubic) crystal system. All trichroic stones, like Tanzanite, all belong to the Orthorombic crystal system, etc. There are 7 crystal systems: Isometric (cubic), Tetragonal, Hexagonal, Trigonal, Orthorombic, Monoclinic and Triclinic.

What is the "Mohs Hardness Scale" all about?

Mohs’ is a scale of the hardness of gems. “Hardness” is defined as a substances resistance to scratching on its surface. Unlike popular belief, it has nothing to do with the gems resistance to breaking. That property is referred to as “Toughness”. Mohs scale is a “relative” scale based upon a material being scratched by either one that is higher up on that scale or one of the same hardness as itself. The scale begins at 1and goes up to 10. Talc is 1, your fingernail is about 2 ½, a knife blade is 6, window glass is 5 ½ . Because this scale is relative, the scale is not even, and by that I mean that the relative hardness of a gem that is 7 is not that much harder than one that is 6, but a diamond that is 10 is almost 162 times harder than ruby that is 9, and ruby is about twice as hard as topaz which is 8. For the general public, any gemstone that is a minimum of 5 is safe to wear in a ring, stones below 5 are best to be worn in earrings or pendants. However, let me quantify that by explaining that “safe to wear” DOES NOT mean that it will never scratch or break. There is no material or substance known in the universe that is indestructible, and that includes all gemstones, including Diamonds!

What is "Refractive Index"?

When light travels through a gemstone, it slows down and changes direction (bent). The degree to which it does this is given a numerical value and that value is called the “refractive index”. It is very important to gemologists as we use this optical property to help us identify one gem from another (it is the most important thing we look at). To you the consumer, the higher the refractive index is, the “brighter” a gem will appear and its flashes of light will appear to be more intense. That is one reason why we like diamonds so much or cubic zirconia, both have high refractive indexes so light is really bent when it travels through the stone allowing for easier facet arrangement that allows for light to be internally reflected “back” to your eye. This is also why a glass stone looks so dead and fake, it has a low refractive index.

What is "Brilliance"?

Brilliance refers to a gems ability to return white light back to the viewers eye. A brilliant gem will look “brighter” and it is usually the result of fine cutting and proportions.

What is "Dispersion"?

This refers to the ability of a gem to “separate” white light into its spectral hues. Remember physics and the passage of light through a prism as it creates a rainbow? That is dispersion, also called “fire”. Some gems are very dispersive like, diamond, cubic zirconia and dementoid garnet. Dispersion can be enhanced by proper gem cutting and proportioning.

What is "Scintillation"?

This is the property that most people call “sparkle”. It simply refers to the amount of light “reflecting” of the surface of a gemstone. One of diamonds most important attributes is that it reflects 17% of white light off its surface, that’s why even a poorer quality diamond can look attractive. Glass reflects only about 5% of white light so it exhibits low scintillation.

Why are gems treated?

Believe it or not, gemstones are not treated in order to “fool” the public. While this may not be the case all the time, it is definitely the case in the vast majority of the time. It is done to help supply and meet the worldwide demand for colored stones and diamonds. The worldwide demand for gemstones is very large and if it where not for enhancing or “treating” gems, the supply would be far short of demand resulting in a situation where only the wealthy could ever afford most gemstones. While I personally love gems that have not been treated, the fact remains that there is far too little of this material available that is affordable so enhancing allows almost anyone to own jewelry set with natural gemstones.

How are gems treated?

There are many ways to enhance or treat a gemstone (both terms are interchangeable). Far too many for me to get into great detail with so I will touch upon the most basic.
Heat Treatment: The vast majority of gems are treated in this manner, usually to remove an unwanted secondary color (like removing the green overtone on Aquamarine, resulting in a purer blue hue). The temperatures and amount of time varies. The treatment is permanent.
Irradiation: Using irradiation, some gems, like tourmaline, can have their colors improved upon. This will NOT give you a radio active gem and it is safe to wear. Many colored diamonds are also irradiated. The treatment is permanent.
Diffusion: This is a process that will diffuse a thin layer of color onto a gemstone. It actually combines on the molecular level so the color is “skin deep”. It is most often used for fancy colored topazes which began life as a natural Topaz with no color and a color is then “diffused” into the gem. It is also used with other gemstones such as sapphire and ruby. The treatment is permanent.
HPHT: This is a high pressure, high heat treatment used to enhance the color of diamonds to make them whiter in color. The treatment is permanent.
Surface Coatings: Usually applied to glass stones and to Topazes to give them unusual colors or iridescent flashes of many hues. Most often applied to the pavilion of the stone ( the underside). Treatment enjoys varying degrees of stability depending on the process.
Dyeing or Staining: As the name implies, it is a process of dyeing stones like we dye fabric. This can only be done on gems that can accept a dye, like pearls, jade, coral and chalcedony are examples of stones which are often dyed. Treatment enjoys varying degrees of stability depending on the process.
Fracture Filling, Oiling and Laser Drilling: These are methods of enhancing the “clarity” of gemstones. Oiling is most often done to emeralds to help hide the cracks that these stones almost always have. Fracture filling is often performed on emeralds and diamonds (though can be done on any gem) and involves various processes of “filling” in surface reaching fractures with a polymer to “mask” the inclusion. Laser drilling is most often done to diamonds and is performed to “reach” a black inclusion within the diamond and then to introduce acid to burn it away. Laser drilling is permanent, oiling is not permanent and will dry up and fracture filling is permanent unless the stone is subjected to heat by a jewelers torch.

Can I tell if the gem is treated?

A gemologist can detect treatment using varying techniques that are tough to us. There are many instances when a gem would have to be sent to a very sophisticated gem lab using high tech equipment in order to detect treatment. For the average consumer, they almost always cannot detect treatment because they are not trained to do so and would not know what to look for.

Does treatment affect value?

The answer is “yes and no”. The world of gemstones is very big. The value of some is affected by treatment while others are not. Some are only affected if it is a certain amount, or kind of treatment. I can definitely say that if a gem is “usually” treated like sapphire, ruby or emerald, and I have a fine example of one that is certified “non-treated”, then that is a very rare stone and will command top dollar. In the case of Blue Topaz or Tanzanite, they would not exist without treatment, so in that case value is not affected at all. In the case of simple heat treatment, aquamarine is not affected. In the case of diamonds, value is affected because there are enough non-treated diamonds available that the public will not pay an equal price for a treated diamond. In the case of emerald, virtually all emeralds are treated, but with this stone it is the degree or amount of treatment that affects value. If the gem has undergone simple oiling, no problem. If the emerald has been heavily impregnated with polymers to hide fissures and fractures, then it commands a lower price, even if it visually appears attractive.

Will the color of my gem ever fade?

Ultraviolet is part of the energy (or natural radiation) that comes from the Sun. Over time, it can fade color in a gem, just like it does to your furniture or color of your car. Luckily for us, most gems can resist the suns fading light. The amount of fading a gem will experience is directly proportional to the amount of time it spends in direct sunlight. For those that live in climates that have the four seasons, this is not so much of a concern. The only two gems that I can think of that you should ever be concerned about is Kunzite and Amethyst, with the emphasis on Kunzite. If you live in a very sunny climate, constant exposure to bright sunlight will fade the color of this gem and also that of Amethyst. There are other gems that can fade somewhat with constant exposure to sunshine, but they are not enough of a problem for me to mention and it is not my intention to needlessly alarm you.

Why do some gems fade and others do not?

The color of gems is caused by color centers in their atomic make up, usually caused by a foreign element that makes up part of the structure of the gem. Ultraviolet light can change the position of electrons thereby causing a loss in color. All gems resist this to varying degrees of success.

What is Pleochroism?

This comes to us from the Greek word of “pleo” meaning “many” and “chroism” meaning “color”. All gemstones that are crystalline and are not part of the Isometric crystal system, will “split” light into two or three beams. We call this dichroic or trichroic, respectively. Due to the fact that each of these beams will be absorbed differently by the gem material, as they exit the stone and hit your eye, you potentially see two or more colors at the same time. This is one of the most attractive aspects of colored gemstones and lends greatly to their visual beauty. Gems, like diamonds, garnet and spinel, are from the Isometric crystal system and are therefore singly refractive, so they naturally do not possess this property.

What is "Selective Absorption"?

When white light enters a gemstone, certain wavelengths of light are absorbed by the medium and the others are allowed to pass through. That is why a blue sapphire is blue and not red. The white light (which is part of the electromagnetic spectrum and which is made up of vibrating energy between 400 and 700 nanometers for visible light) is absorbed, but for the energy near the “blue” end of the spectrum, or that which is around 400 to 450 nanometer, this passes through and this is what we end up seeing. This is why we see color, not only in gems, but in all materials.

Why do gemstones have color?

Most gemstones are “allochromatic”. That is to say that in their pure state, they have no color at all and are clear like glass. It is the presence of elemental impurities present in the crystal make up that gives the gem its color. Pure Corundum has no color, but when containing a trace of Chromium, you get the red of Ruby, or a trace of Titanium and Iron, the blue of Blue Sapphire. Some gems are “idiochromatic” so the coloring element is actually an essential part of its make up and without which, it would not longer be that gem. Malachite is an example of such.

What is "Specific Gravity"?

This is another tool used to help identify gem materials. Imagine having one cubic inch of sapphire and another cubic inch of water. The sapphire (or Corundum) would weigh four times as much as the equal volume of water. Therefore we assign the specific gravity of sapphire as “4”. The specific gravity of Quartz is 2.65 etc.

Can my gem look different in under different lights?

Yes it can and so do you! Natural sunlight is made up of the full spectrum of visible light which is 400 to 700 nanometers. Artificial light that we use to light up our lives is rarely as even. Fluorescent lights usually lean toward the blue end of the spectrum while incandescent light bulbs lean over to the red end. So when viewing certain colored gems, their appearance can be enhanced or unenhanced by the light that is present when viewing the stone. The best light is good old sunshine, second to that would be the quartz halogen lights used by many retailers. The reason the gem is affected by this is that it is only exposed to part of the full spectrum, so it can only work with the light it is given. When exposed to full sunlight, it gets to show off its true colors. Everything looks better in the sun, even gems!

What are "Inclusions or Flaws"?

Inclusions also known as flaws are internal clarity characteristics that are the remnants of the gem forming process. As gems are forming and crystallizing, they are being subjected to immense natural forces and foreign materials, all at the same time. As they form, some of these can become trapped within the stone. There are essentially two different types of inclusions: internal foreign material in the form of other crystals or minerals, and, internal voids, cracks or fissures which are in essence a separation of the gem material itself. They are all a natural part of the gem and are indicative of natural origin.

Do flaws or inclusions mean I have a poor stone?

It all depends upon the stone and to what degree (how many and what type) of inclusions you have. No gem is truly flawless. Flawless diamonds are only flawless under 10X magnification and may show an inclusion under 50X! In gems that are normally heavily included (type III stones) we are more lenient with inclusions and do not downgrade the gem so much because of it. Emerald is the perfect example, another is Rubellite. These gems are normally heavily included so it is not a big deal to see flaws inside these stones. Aquamarine though is a Type I stone, so we expect to see a very clean, clear specimen. If we do not, then the gem is much less valuable. Blue Topaz is another gem that is normally very clean. Judging clarity characteristics takes professional gemological training so it is impossible for me to go into any detail in such a format. Suffice to say that when you look inside a gem, seeing something is usually not the big deal that most people think it is. It usually just means you have a natural gem and not a gem made by man. The problem with flaws is in its “name” and not in what it really is. This is why we prefer to use the more accurate term of “inclusion”. When the word “flaw” is used to describe or talk about anything, it immediately implies something bad which is the reason “flaws” are so feared (and needlessly so) by so many.

What is a jeweler's loupe?

A jewelers loupe is an optical magnifier which is fully corrected for spherical and chromatic aberrations. That’s a fancy way of saying that when it magnifies, it gives a true representation of what you are seeing and doesn’t add or subtract anything. This is accomplished by using a “sandwich” of three lenses, the middle being a blubish shape and the outer two being concave on one side and convex on the other side. This is why these loupes are also referred to as a “triplet”.

Does cutting and polishing quality affect value?

Yes and no. In the vast kingdom of gems, all the rules don’t apply to all the gems, all the time! To put it simply, when purchasing a relatively expensive gem like Diamond, Emerald, Ruby, Fine Tourmaline or Tanzanite, fine cutting quality and polishing will put a premium on the stone for two reasons. Primarily, these gems are held in high esteem and are sought after so the public will pay more for a finer cut and polish. Secondly, finer cutting and polishing will visibly improve the quality and look of those gems, especially diamond. When it comes to very inexpensive stones like glass or other imitation gems (with the exception of CZ), or obscure, low quality gems with little or no color, the industry and the public do not place much value on these gems so no one really cares how well the stone is polished or cut. That is why our industry will not put in the extra cost to achieve a fine polish when no one will support it in the price paid.

What are the main gemstones of the world?

You are probably already familiar with the main gemstones of the world. By definition, they are the most sold and the most well known (but not necessarily the most valuable, or the rarest). I will list the most popular: Diamond, Ruby, Sapphire, Emerald, the Garnet Group, Amethyst, Citrine, the Tourmaline family, Tanzanite, All Pearls, Opals, Peridot, Iolite, Zircons, Aquamarine, Morganite, Yellow Beryl, Imperial Topaz, Blue Topaz, the Diopside family, Kunzite, the Spinel family. The list is for natural gems, of course there are a wide variety of popular man-made gems like CZ that we have not listed.

Does mining location affect value?

No it does not. It is more accurate to say that it is usual for certain consistent quality of gemstones to mined in certain geographical regions. So we tend to “expect” a ruby from Burma to look a certain way and to be of a certain quality, BUT, mining location DOES NOT automatically mean that EVERY gem from that region is of the quality that you expect. You do get bad rubies from Burma and you also can get poor amethyst from Tanzania, but you usually do not. Gemologists are trained to objectively judge a gem by its quality and not by its location. A poor quality Peridot is of little interest to me or my customers and I do not care if it came from Arizona or China or the Moon! A fine flawless diamond is worth a great deal of money no matter where it is mined from.

How are jewelry appraisals done?

I was a jewelry appraiser for years so I’ll tell you how I, and others I know, did them. We looked at the item and gave it a general description. We then begin to systematically identify, measure (so we can estimate the gem weight by formulae) and grade each gemstone in the piece. We then weigh the entire item and then subtract the gem weight from the item weight of the entire piece to obtain the mount weight. We then identify the metal as gold, or silver etc. and then determine the karatage. By using various price lists and guides we calculate the price of the gemstones and the cost of the mounting. We then add an estimate for workmanship in the item. We add all this up and then apply a markup to obtain one of many values depending on what purpose the appraisal will serve, such as estate, insurance replacement, retail value, etc. We put all this on paper with a photo.

Who can do jewelry appraisals?

This all depends on local laws and regulations (if any apply or exist) in your region of the country. It is safe to say that whoever does jewelry appraisal should have a background in the jewelry industry and be able to identify gemstones and have access to current market conditions. This often implies gemological training.

Why do appraisals differ on the same item?

Different people will see the same thing differently. Even two gemologists that graduated at the same time from the same class, can grade the clarity of a diamond differently. There is a “subjective” element when it comes to gemstone “grading” but not to gemstone “identification” (a ruby is a ruby, there is not question about that). In addition to this, appraisers can utilize different price guides in determining the cost of gemstones and they may not all be familiar with new gemstones (like Tashmarine) that have just hit the market. They can also apply different markup percentages to the item, that when taken all together, can give you two different values.

What is Gold?

Gold is a precious metal. It is the most famous precious metal in the world and throughout history. It has been revered not only for its lovely golden yellow hue, but because it possess some very unique properties that make it stand out from other metals. Gold is a metal which is an element. It is very stable and will not tarnish. It is very “ductile” and by that we mean it can be “stretched” out into a very thin wire the width of a human hair without breaking! It is also very “malleable”, and by that we mean it can be pounded down and made so thin that you can actually see through it!, all without breaking apart! We have all seen “gold leaf” used on the edge of books or on architecture such as molding. This is real 24K gold that has been pounded down and made so thin it is applied directly to a surface. Gold has an atomic weight of 196.967 and a specific gravity of 19.32. It is one of the few natural things that is recognized worldwide by almost everyone and one of the few items that has held it’s value consistently throughout history.
Gold is traded worldwide and it’s price is determined by the London Fix which is a twice daily pricing of the gold market in which the asking and selling prices are determined. Gold is then traded worldwide based upon this price. For jewelry, gold is most often “alloyed” with other metals because pure gold bullion (24K) is often too soft for the needs of jewelry, so it is mixed with other metals making the Karat gold that we are all familiar with. This also makes it much more affordable.
The term “Karat” refers to the amount of pure gold contained within an item, versus the amount of alloy or other metal it contains. The karats that you may encounter are as follows:

24K - 100% pure gold, no alloy
22K - 91.66% pure gold, 8.34% alloy
18K - 75% pure gold, 25% alloy
14K - 58.33% pure gold, 41.67% alloy
10K - 41.66% pure gold, 58.34% alloy

The color of gold can be changed by using different alloy metals. So when we make 14K gold jewelry, we can alter the final color that give the item a totally different look, but still preserves the valuable gold content. We can make 14K yellow gold by using brass in our mixture of alloy, we can make 14K white gold by using nickel or palladium, we can make 14k rose gold by using copper or 14K green gold by using silver or even turn it blue by using aluminum as the alloying agent.

What does "Carat" mean?

This is a measurement system used worldwide to communicate the weight of gemstones. A carat was traditionally based upon the weight of the ancient “carab” seed which is very constant in size and weight. Ancient dealers used to use these as “counterweights” on balances in order to determine how many seeds was equal to in weight to an item on the other side of the balance. Today, the term “carat” is part of the metric system of weights and equals one fifth of a gram. Five carats therefore equals one full gram. There are 155.517 carats in one troy ounce. Carats are further broken down into “points” of 100 “points” per carat, just like the dollar is divided into 100 cents. So when you buy any gemstone, its weight will be communicated in “carats” and will be given with a main number, followed by a decimal and two other digits, for example: 1.21 ct (ct is the short form for carats), 0.56ct, 15.99ct etc .

What is Silver?

Silver is another very famous precious metal which traces its history throughout antiquity. It is usually alloyed when used in jewelry and is sold as “sterling silver” which is 92.5% pure silver with the balance being made up of any alloy. It, like gold, has unique properties.


What is Platinum and the Platinum Group of Metals?

Platinum is the most expensive precious metal and is regarded as a relatively new metal but has been know historically as infant silver by the Spanish who used to through it back into the sea to finish ripening. Platinum has some very unique properties and is used extensively throughout industry, not just in jewelry. It is a catalyst metal and can withstand very high temperatures which is why it is used in catalytic converters and is instrumental in lab creating gemstones. In jewelry, Platinum is the best metal to set gemstones into because it is very durable and has “no memory”. By memory, we mean that when a prong of gold is bent down to hold a gem in place, it wants to come back up to its original position. Platinum will stay put and never move on its own. It is very common for a well made Platinum ring to last 100 years! Platinum is in a group of metals that are called the Platinum group of metals because they are so closely related, that up until the 19th Century, they where all considered the same metal. The other members of this closely elated group are Rhodium, Osmium, Ruthenium, Palladium, Iridium. The main difference is that these metals have different Atomic Weights, so we know that they are separate. When Platinum is found in nature, it is almost always combined or mixed in with these other members of this precious family. The refining process is very long and time consuming for Platinum because it must be separated from these other metals. The process can take 6 months which is the main reason why Platinum is so expensive. Gold is much rarer than Platinum but Gold is fairly easy to refine (it can be done in your garage) while Platinum is a big deal to refine but is more plentiful in nature


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