There are three tasks in gem identification :-

A. What is it
B. Is it natural or synthetic
C. What type of enhancement (if any) has it had

To illustrate we see a red transparent stone, let's say a round brilliant, that is very sparkly and has no eye-visible inclusions:

A. What is it :

This is the easiest of all for a gemologist to answer, as red glass, natural red spinel, natural red garnet, natural ruby, synthetic ruby, and many other gems can look like this, but they will differ in optical, physical and chemical properties such as refractive index, optic character, density, fluorescence, pleochroism, hardness, etc. So we test it and rule out all the major possibilities except ruby. But is it natural or synthetic we don't know yet as a synthetic ruby is ruby and has all the same readings as a natural one. On to question two:

B. Natural or synthetic :

There are many types of synthetic rubies and some are relatively easy to spot with a trained eye and the right equipment (a gemological microscope with immersion liquids and/or diffused lighting). For example, if we see internal structures under magnification called "curved striae" end of story, the stone is a synthetic ruby. If we see a microscopic inclusion of a sort called a "fingerprint" we have a natural stone. But, what if the stone is flawless or if the inclusions are ambiguous can be seen in either natural or synthetic (very commonly this is the case). At that point a big gem lab with expensive high tech equipment may be the only way to get an accurate ID.

C. Is it enhanced :

Let's say we determine that we have a ruby of natural origin. It still may have been enhanced by heat, diffusion, coating, filling or other methods to improve its clarity and color. Again, some of these treatments are easy to spot if you have the equipment and knowledge, some are not. For example, an inclusion called a stress fracture is indicative of heating and a fine and intact network of rutile fibers indicates no heat, but there is a great middle ground here too, where it can be very difficult to determine the enhancement status of a gem.

Treatments of Gemstones :-

Story behind this treatment :

Heating of gemstones to enhance their color goes back centuries. It is considered a natural type of treatment since the process is basically a continuation of the processes that occur in the ground. The stone is heated to a very high temperature, which causes the inclusions (ref. Why Gemstones Have Color in Colored Gemstones 101) to reform themselves and improve the color by making darker, lighter, more intense, or of a different color. It has been properly stated that without heat treatment the world would be without many colored gemstones. Because colored gemstones occurring in the colors we see are very rare. But heating can take an off-color stone and turn it into a beautiful gemstone. So don't be worried about heat treatment.

Can I wear it every day :

Heat treatment, for the most part, is permanent. As in the case of the tanzanite shown above. This stone is a brown color coming out of the ground. But turns a beautiful blue/purple (shown at left) after heating. The few exceptions would be kunzite which will tend to fade from its medium pink color to light pink and then colorless in daylight (which is why it’s called the midnight stone), and yellow sapphire, which can also fade when exposed to direct sunlight.

What does this treatment do to the stone :

Basically, it rearranges the atoms in the gemstone. Sometimes, as in the case of ruby, the stone is heated almost to a point of melting, which lets the aluminum oxide in the stone reform to what is basically a new crystal structure. This lets the chromium reform to give off a better color of red. The same can apply to a type of sapphire known as gouda sapphires. These are milky white sapphires that turn blue, and account for many of the promotional quality sapphires out on the market today.

Does this treatment save money :

Oh Yeah! For instance, a 3.00 carat fine blue sapphire of natural, unheated color can sell for as much as US$20,000.00, while a heated stone of the same color can go for as little as $1500.00. Which means that you will always want to have a proper gemological evaluation for any sapphires, ruby, etc...that you buy.

What do I need to know before going shopping :

Always stay with a professional, independent jeweller with some serious gemological training. There can be a HUGE price difference in two gemstones that appear the same color and clarity due to heat treatment. And it takes someone with some good experience and good gemological knowledge to be able to identify one from the other. So stay with someone with a good reputation for quality, and someone who handles enough gemstones to be able to have some good connections with colored gemstone suppliers.

Note: Stay away from the discount stores like Service Merchandise, Sams, Walmart, etc...when shopping for fine quality colored gemstones. And for that matter...stay away from most of the Internet sellers. Colored gemstone shopping is "business for the eyes" as a good friend from Israel once told me. You can't buy a quality gemstone from someone claiming discounts, and you can't buy a quality gemstone based on a picture on your computer screen. Stay with a local professional jeweller. Fine qualities colored gemstones are never discounted because they are too rare. And buying a colored gemstone without seeing what it looks like to your own eyes is buy what we in Texas call a "pig in a poke." If you can't see it, you won't know what you got until you get home with it. And then it’s too late.

Gemological Information :-

Special Identifying Properties and Tests :

There are a number of ways to identify heat treatment in sapphires. One is the easy way to find the halo effect around included crystals. This is where the inclusions caused fracturing of the stone when the heat was applied. Also (which is now taught to you GIA Graduate Gemologist...unfortunately) heated blue sapphires will generally lose their iron spectrum lines in the 4400 to 4500 region. Natural blue sapphires will generally have nice absorption lines in this region to due iron content. This is not diagnostic but I can tell you that I have not seen the absorption bands in heated sapphires. And the absence of these lines will also serve as a signpost that you might have a synthetic. But a nice strong line in the 4500 will be a strong case for a natural blue that is not treated by heat.

The fact is, most gemstones used in jewelry have been treated to improve their appearance. Treated gemstones can be a good choice, because they should be more affordable than untreated stones that achieve their quality naturally. Do you know what the common treatments are? Some last forever, some don't.

Before you buy a colored gemstone, ask if it's been treated.

Types of Gemstone Treatments :

  • Heat and radiation is often used to change or enhance gemstone colors.
  • Diffusion is used to deepen a gem's color. Diffusion only intensifies a gemstone's outer layers.
  • Oil and waxes enhance gemstone colors by filling-in fine surface cracks, blending them away temporarily.
  • Fracture filling coats gems with a clear or colored epoxy resin or another substance. The treatment fills-in cracks, which improves the appearance of the gemstone.
  • Laser drilling removes inclusions, improving clarity.
    If any form of the word enhanced is used in ads or disclosures, the gem has been treated in some way.
Are Gemstone treatments permanent :

Some gemstone treatments are permanent, but others are not. Heat treatments can go either way, because they create permanent color changes in some gems -- temporary changes in others.

Gems are treated in different ways to improve their appearance. Some of these procedures are centuries old, while others are relatively new. Within the industry, some of these practices are taken as commonplace, while the gem buying public's awareness of these treatments has been much lower.

In this day of full disclosure and public awareness, the subject is coming to the forefront. Many industry officials are concerned that too much information will confuse customers and hurt sales. Others feel the public's right to know outweighs these concerns.

One certainly can confuse the public, as gem enhancement covers such difficult subjects as the physics of light response to molecular structure. However, some general comments are in order.
First, let me clarify that the term "natural gems" refers to those formed in the earth, whether or not they have been treated after mining. This, in contrast to "lab created," "man made" or "synthetic" gems.

The most common form of enhancement is heat treating. This is so common with corundum, (ruby and sapphire,) it is recommended that jewelers inform their customers that they are "probably heat treated."

"Probably" That doesn't sound very professional. What is happening here is that the procedure so closely resembles what happens in nature that one can't always tell if they have been treated after mining. Microscopic examination will sometimes reveal evidence of heating, but lacking that there is no way to tell if the heat treatment was done before or after mining.

A similar situation occurs with aquamarine. If properly heated, it will lose its green tint and become a pure blue. This is also identical to what happens in nature and there is no way of telling if it was done after mining. However, since most of the material coming out of the ground does have a green tint, it is recommended that the pure blue gems are described as "probably heat treated."

Very closely related to this is the treatment of blue topaz. Actually, it is a treatment of colorless topaz to turn them blue. This is done in two steps. First the rough is subjected to radiation to modify the sharing of electrons between certain atoms in the crystal structure. This turns the topaz brown. Then they are heated to become a stable blue color.

"Radiation" Yes, this is one of the reason industry officials are reluctant to use full disclosure. Radiation is a scary word and telling someone a gem has exposed to it will certainly drive customers away.

However, this too exactly duplicates what happens in nature. Many gem crystals get exposed to radioactive elements during their formation. That doesn't mean they become radioactive, nor does it imply anything else. In fact, many gems seem to have beneficial effects on their wearers.

The above represent some of the most common examples of gem enhancement. The industry has never felt a need to disclose treatments that are indistinguishable from the processes that occur in natural formation. However, there is one other common enhancement that falls into an entirely different category. That is the oiling of stones.

Some gems, most notably emeralds, have internal fractures. Light reflects off of their surfaces, which seriously affects the clarity and brilliance of the gem. However, by simply filling them with a substance of similar optical properties, the tiny cavities once again become transparent. The difference in the appearance of the finished gem can often be startling.

Now, how chicken this is depends on your point of view. To the gem cutter, this is a serious problem. Those tiny fractures represent areas of weakness that have to be considered in the cutting process. If masked with oil, the risk of damage during cutting becomes much greater.

To the proud owner of an emerald, the improvement to its appearance is well worth it. One doesn't see the oil; it simply allows the natural beauty of the gemstone to stand out. Both the emotional and the monetary value of the gem are considerably enhanced.

However, the owner should certainly be made aware that it needs special care. Continual washing of dishes while wearing an emerald ring can cause it to lose its brilliance. Vigorous cleaning methods, like using heat or immersing in an ultrasonic jewelry cleaner can be disastrous.

There are many other ways gems can be enhanced. Inexpensive ones are often dyed, the porosity of turquoise is often sealed so body oils don't discolor them, etc. However, the above represent the most common examples one is likely to come across.

Crystals vs Gemstones :-

Gem is a rare mineral that is highly priced. Gems are beautiful stones that are used in making jewelry. Crystals are pure substances that have molecules arranged in a regular geometric pattern.

A gem can be a crystal whereas a crystal will not always be a gem.

Gems can have mineral bases such as ruby or diamond and an organic base such as amber.
Crystals are solids that have atoms, ions and molecules fixed in a regular order, which extend in three dimensions. Crystals can also be defined as objects that have well-defined geometric shapes.

Gem is also known as gemstone that can be precious or semi precious that is cut and polished to be used in jewelry. The precious gems include diamond, sapphire, ruby and emerald and all other gems are considered to be semi-precious.

Gems can be classified according to the chemical composition gemstone and the crystal structure. Crystals are mainly classified as cubic, hexagonal, tetragonal, orthorhombic, monoclinic and rhombohedral.

When comparing the value of crystals and gems, the latter ones are priced more. Almost everything related to minerals can be termed as crystals as they have specific properties. When comparing the hardness, specific gravity, refractive index, durability and fluorescence, the crystals are different from the gems. One thing that has to be noted is that different gems have different properties as different crystals having different properties.

When comparing the color between gems and crystals, the gems come in various colors like red, green and blue. The crystals also come in colors according to the transmission of light through them.

Summary :

1. A gem can be a crystal whereas a crystal will not always be a gem.

2. Gems can be mineral based such as ruby or diamond and organic based such as amber.

3. Crystals are solids that have atoms, ions and molecules fixed in a regular order, which extend in three dimensions.

4. Gem is also known as gemstone that can be precious or semi precious that is cut and polished to be used in jewelry.

5. Gems can be classified according to the chemical composition gemstone and the crystal structure. Crystals are mainly classified as cubic, hexagonal, tetragonal, orthorhombic, monoclinic and rhombohedral.

6. When comparing the value of crystals and gems, the latter ones are priced more.

7. One thing that has to be noted is that different gems have different properties like different crystals having different properties.