How To Choose A Gemstone

Before you go to the step of buying a natural gemstone you should first make sure that the stone is living up to your expectations. The gemstone industry is huge and where there is a lot of money changing hands there is bound to be criminal minds involved as well.
Reading ads on gemstones and gemstone jewelry can be confusing. Gemstones may be labeled as natural, genuine, synthetic, simulated, treated, imitation etc.

Natural Gemstones

These are stones from crystal deposits formed by nature and polished and cut into various sizes and shapes. No other treatment of the stones is carried out.

Genuine Gemstones

These are also stones made from crystals found in the nature but has been treated in some way. The widely accepted treatments are those which alter the whole stone permanently.

Below I have listed some of the most common ways to improve the looks or durability of gemstones.

Heat treatment

Heat can change or enhance the color of a gemstone and is regarded as a natural type of enhancement and therefore approved by the gemstone industry.
The temperature used is quite high, about 1600 degrees Celsius.
The heat will change the state of the impurities in the stone and the result may be a darker or lighter color, more intense color or change the stone to a different color altogether.

Examples may be Amethyst that can change the color to yellow and appear as Citrine.
Aquamarine may get rid of the common greenish tone and become more “pure” blue.
Other stones like Ruby, Sapphire, Tanzanite, Topaz, Tourmaline and Zircon is also often going through heat treatment.

Diffusion treatment

The stone will here be exposed to some chemicals and heated up.
This method is a bit controversial as the color enhancement will, generally, only reach the surface of the stone and may penetrate up to half a millimeter into the stone. If the stone has to be recut after treatment the value of it will drop significantly.
It is widely accepted to enhance Star Sapphires in this way as the physical properties of the stone is not affected, only the “star” effect.

Beryllium treatment

This is a relatively new type of treatment that is used mainly for treating Sapphire.
It is a heat treatment where Beryllium is added in. Beryllium is a well-known element which is essential in many gemstones from nature.
The enhancement goes much deeper into the stone than with the traditional diffusion method and the stone can be polished and cut if needed.
Bright yellow and orange Sapphire may be produced by this method and can give a very brilliant and beautiful result.

Fracture filling

Very often natural gemstones may have small cracks that interfere with the light passing through the stone.
If these cracks goes all the way to the surface of the stone they may be filled with various material such as oil, wax, glass, epoxy or borax in order to enhance the ability to pass light through the stone.

Be especially aware of this practice when considering gemstones like Aquamarine, Peridot, Ruby, Sapphire and Turquoise.
Emerald is accepted to be treated in this way as these stones are very commonly fractured from nature and would not look very nice without some kind of treatment.

Lately, Rubies have been successfully treated with crystal glass (lead glass) which has practically the same refractive index (the way light travels through an object) as the stone itself.
These stones are quite durable but some precautions should be taken when cleaning the stones.

Irradiation treatment:

This is a very common method used to produce Blue Topaz which is very rare in nature.
Clear Topaz is “bombarded” with large doses of electrons from a linear accelerator or they are exposed to neutrons from a nuclear reactor.
The radioactivity left in the stone through this treatment will have a short lifespan and various government agencies specify strict regulations on companies performing this treatment to make sure that no stone reaches the public unless it is safe.

Practically all Blue Topaz stones are a result of this treatment and depending on the processing methods used the end result can vary. The more common denominations of the processed Topaz stones are “Sky Blue”, “Swiss Blue” and “London Blue” where the last one is the most expensive type as neutrons have been used to enhance the color and this is an expensive process.
Other color variations have got additional trade names.

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Many of the treatments used to enhance or change a gemstone’s appearance are difficult to observe with the naked eye but is fairly easy to detect for a professional gemologist with the proper equipment.
All serious dealers are revealing whether or not a gemstone has been treated, but if you are in doubt, ask for a certificate for the stone. This will usually cost around US $20.- or in that range.

Synthetic Gemstones

Synthetic gemstones must not be confused with fake gemstones as they have the same basic crystal structure, color and other characteristics as the natural gemstones. The main difference is that they but they have been grown in a laboratory and not formed by nature.
Sometimes it is difficult even for gemologists to find out whether or not a stone is natural or synthetic, and the stone has to be sent to an accredited laboratory to separate the synthetic from the natural.

The main difference is in the price, a synthetic gemstone cost much less than a natural one and this should be reflected in the selling price, so actually it is nothing wrong in choosing a synthetic gemstone over one that is formed by nature as long as you don’t pay the price for a natural gemstone.

Common synthetic gemstones are Alexandrite, Amethyst, Diamond, Emerald, Opal, Ruby, Sapphire and Spinel.

However, especially Emerald gemstones are quite costly to produce in a laboratory and the difference in price between a natural produced stone and a laboratory grown one may be less than for some of the others.
Actually a laboratory grown Emerald may be preferred over a naturally formed one as it can be made more perfect with less inclusions.

Simulated, or Imitation, Gemstones

These stones are also created in a laboratory but are different from natural and synthetic gemstones.
The mineral composition, color, hardness or looks are often the most significant differences.

They may be made from many different materials like plastic, glass and even other natural stones. Simulated Alexandrites are often made from color-change, synthetic, Sapphires.
Simulated Opal may be made of plastic or glass and many different stones may be simulated by synthetic Spinel as they can come in many different colors.

Simulated, or imitation, stones are very often found in fashion jewelry but sometimes sellers may try to pass simulated stones off as natural gemstones.
The main thing is not to avoid buying laboratory produced stones, but to ensure that you don’t overpay for the gemstone you purchase.

If you intend to spend a large amount of money on a certain gemstone and you don’t know the seller, or have strong evidence to believe he/she is trustworthy, ask the seller to explain to you how he knows the gemstone in question is real and not a simulated stone.

Some manufacturers of imitation gemstones, including pearls, are very serious and honest with regards to what they deliver, like the Austrian company SWAROVSKI . Their products are of a high quality compared to many other manufacturers and held in high regard around the world.
Prices are very clearly reflecting the fact that these are imitations of the “real thing”.

One advise that I believe is worthwhile to take note of is to avoid “the world of sharks” when purchasing gemstones. This may be represented by the very popular site “Ebay”. Anybody may offer anything, and they usually do, for any price they can get. Be very careful when you intend to buy expensive natural gemstones on this kind of sites.

Decision Time

It may be difficult to decide on the purchase of gemstones if you don’t have “unlimited” funds and expert knowledge.

You may also take into consideration the durability of the various gemstones. This depends largely on the hardness of the stone besides the cleavage. Cleavage means the stone can be split easily when knocking in the “right” spot on the stone and thereby damage it.

The gemstones on top of the hardness scale are Diamond, Ruby and Sapphire which have a hardness of 9-10. These stones are also less prone to be split by the wearer, although diamonds are a bit more prone to cleavage than the other two. The risk of cleavage is mainly a concern during processing of the stone and the three stones mentioned is very resistant to scratches etc. and therefore durable enough for everyday wear.
Also Alexandrite, Chrysoberyl and Spinel is classified as durable enough for everyday wear.

This should not scare you away from choosing other types of stones it just means you should be more careful when wearing some stones to avoid scratches etc. Most gemstones have a hardness above steel blades.

However, besides what is mentioned above, when buying a gemstone you would definitely consider the three C's: Color, Clarity, Cut and the always important - Your Likes and Dislikes.

Color

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The more vivid a stone appears the more attention it grabs and, therefore, the higher the value.
“Hue”, “Saturation” and “Tone” are often used to describe how the color of a stone appears to our eyesight.

“Hue” is the unique color of the stone, i.e. what kind of color group it belongs to like “blue”, “green” and so on. Most often gemstones have shades of various colors but the most valuable ones are those with a pure color without inclusions of others.

“Saturation” means the intensity, or purity, of the color. The more intense, or pure, the color is, the higher the value.

“Tone” means the strength, or depth, of the color (“Hue”). It can range from practically colorless to total dark, or black.
The range is from “light” to “medium light” to “medium” to “ medium-dark” to “dark”.
The most attractive tone, and the often the most valuable is considered to be between “medium-light” to “medium-dark”.

Clarity

Clarity means whether the gemstone has any flaws as inclusions of various minerals that may be seen with the naked eye or through a microscope. There may also be minor cracks or other imperfections in the stone that affects the value.

Smaller imperfections are common and does not affect the value very much as long as they do not distract the eye or interfere with the light reflection etc. to any large degree.
Perfect natural gemstones are very rare and the value is extremely high.
If you come across a seemingly perfect gemstone, be aware that it may be a stone that has been produced in a laboratory and not one formed by nature.

The clarity is graded differently for colored gemstones as compared to diamonds and are divided into three different types of grading depending on type of gemstone.

Type 1
Stones that usually have very small or no inclusions like Aquamarine, Chrysoberyl, Blue Topaz, Blue Zircon, Morganite, Tanzanite and Green Tourmaline.

Type 2
Stones that usually have some inclusions like Alexandrite, Amethyst, Citrine, Garnets, Peridot, Ruby, Sapphire, Spinel, Tourmaline (except green, red and watermelon) and Zircon (except blue).

Type 3
Stones that practically always have inclusions like Emerald, Red Beryl, Tourmaline (red and watermelon). These three groups are further divided up into more specific categories with regards to the visibility of inclusions:

Type 1
Type 2 Type3
VVS Not detected by the naked eye, and difficult to see 10 times enlarged Usually not detectable with the naked eye but can be seen with 10 times enlargement Usually not detectable with the naked eye but noticeable with 10 times enlargement
VS Usually not detectable with the naked eye but easy to see with 10x enlargement May be seen with the naked eye and are noticeable with 10x enlargement May be seen with the naked eye and are very easy to see with 10x enlargement
SI1 May be seen with the naked eye and very noticeable with 10x enlargement Easy to see with the naked eye and obvious with 10x enlargement Is obvious to the naked eye
SI2 Easily seen with the naked eye Very easily seen by the naked eye Very obvious to the naked eye
I1 Affecting appearance or durability Affecting appearance or durability Affecting appearance or durability
I2 Seriously affecting appearance or durability Seriously affecting appearance or durability Seriously affecting appearance or durability
I3 Seriously affecting both appearance and durability Seriously affecting both appearance and durability Seriously affecting both appearance and durability
DcI No transparency No transparency No transparency

Cut

There are many different ways to cut a colored gemstone and it takes a lot of experience to get a stone cut in a way that optimizes it’s brilliance.

The cut has to be symmetrical so that light reflects evenly across the surface when it is held with the face up.
If the stone seems to be too dark it may be that the cutting has been too deep and narrow.
If the stone seems a bit lifeless it may be due to a shallow and wide cutting.

When a gemstone has a high grade of saturation it is advisable to cut it a bit shallow in order to allow more light to be passed and if it is less saturated a deeper cut may increase the stones vividness.
However, there does not exist any absolute rules for cutting gemstones, therefore experience and skills are the main factors that can heavily influence the result when cutting a gemstone.

Some simple guidelines exist, though, with regards to calibrated sizes and general types of cutting. This is in order for easy mounting in standardized mountings.
The weight in carat may not be equal to a certain size as different stones can have different densities.

Some of the various standard cuts and standard measurements can be seen below. Other sizes can also be found for most stones, smaller and/or larger, and also with calibrated measurements in between the standard sizes mentioned.
When buying gemstones to insert into a standard, readymade, mounting, be sure to get the size of the stone as close as possible to the size of the finding.

Here shown for the gemstone Amethyst

Type of Cut
Image
Some Calibrated sizes
Comments
Round
2 mm
2.5 mm
3 mm
3.5 mm
4 mm
5 mm
6 mm
6.5 mm
7 mm
8 mm
9 mm
10 mm
11 mm
12 mm
13 mm
14 mm
15 mm
Approximately 57 facets.
Optically this cut is the most efficient and was originally developed for Diamonds, but is now used for all kinds of gem stones.
Oval
5 x 3 mm
6 x 4 mm
7 x 5 mm
8 x 6 mm
9 x 7 mm
10 x 8 mm
11 x 9 mm
12 x 10 mm
14 x 10 mm
14 x 12 mm
16 x 12 mm
18 x 13 mm
20 x 15 mm
Approximately 69 facets.
Elliptical shape when viewed from top.
Emerald
5 x 3 mm
6 x 4 mm
7 x 5 mm
8 x 6 mm
9 x 7 mm
10 x 8 mm
11 x 9 mm
12 x 10 mm
14 x 12 mm
16 x 12 mm
18 x 13 mm
20 x 15 mm
25 x 18 mm
27 x 20 mm
30 x 22 mm
Approximately 50 facets.
Rectangular or square step cut with diagonal corners.
Antique Cushion
6 x 4 mm
7 x 5 mm
8 x 6 mm
9 x 7 mm
10 x 8 mm
11 x 9 mm
12 x 10 mm
14 x 10 mm
14 x 12 mm
Approximately 64 facets.
Common in the late 19th and the early 20th centuries.
Known under different names like “The Old Miner Cut” etc.
It is a very brilliant cut.
Heart
5 x 5 mm
6 x 6 mm
7 x 7 mm
8 x 8 mm
9 x 9 mm
10 x 10 mm
11 x 11 mm
12 x 12 mm
13 x 13 mm
Approximately 59 facets.
A pear shape with a cleft at the top.
The size is often 1.1:1 in favour of the length.
Due to the necessity to cut a heart extremely accurate, the price is slightly higher than for other types.
Baguette
From 1 to 3.50 mm wide in steps of 0.50 mm
and
from 1.50 to 5 mm long in steps of 0.5 mm
Approximately 20 facets.
Like the square cut, the facets are cut in steps, parallel to the edges
Square
4 x 4 mm
5 x 5 mm
6 x 6 mm
7 x 7 mm
8 x 8 mm
9 x 9 mm
10 x 10 mm
11 x 11 mm
12 x 12 mm
13 x 13 mm
14 x 14 mm
Approximately 57 facets.
Like the Baguette cut, the facets are cut in steps, parallel to the edges.
Princess
4 x 4 mm
5 x 5 mm
6 x 6 mm
7 x 7 mm
8 x 8 mm
9 x 9 mm
10 x 10 mm
11 x 11 mm
12 x 12 mm
13 x 13 mm
14 x 14 mm
Approximately 76 facets.
Princess cut is technically known as “Square Modified Brilliant” and is a square version of the round brilliant cut with numerous sparkling facets.
It is a very brilliant and sparkling cut.
Pear
5 x 3 mm
6 x 4 mm
7 x 5 mm
8 x 6 mm
9 x 6 mm
10 x 7 mm
12 x 8 mm
13 x 9 mm
14 x 9 mm
15 x 10 mm
16 x 12 mm
18 x 13 mm
20 x 15 mm
Approximately 71 facets.
Pear or Teardrop cut is asymmetrical cut with one pointed and one rounded end. A hybrid cut, combining the best of the oval and the marquise, it is shaped like a sparkling teardrop.
Trillion
4 x 4 mm
5 x 5 mm
6 x 6 mm
7 x 7 mm
8 x 8 mm
9 x 9 mm
10 x 10 mm
11 x 11 mm
12 x 12 mm
13 x 13 mm
14 x 14 mm
15 x 15 mm
16 x 16 mm
Approximately 44 facets.
Trillion, or Trilliant, cut is a triangular shape.
It returns lots of light and color and therefor a good choice for lighter colored stones.
Briolette
Briolette come in many different sizes
from
4-40 mm length and
3-20 mm diameter
but most commonly
6-12 mm length and
3-8 mm diameter
Approximately 84 facets.
This is the most difficult shape to cut.
It may be cut with a round diameter or an oval shape when seen from top.
Marquise
4 x 2 mm
5 x 2.5 mm
5 x 3 mm
6 x 3 mm
7 x 3.5 mm
8 x 4 mm
10 x 5 mm
12 x 6 mm
14 x 7 mm
16 x 8 mm
18 x 9 mm
20 x 10 mm
Approximately 57 facets.
It looks a bit like a rugby ball or a boat shape.
Generally the ratio between length and with is 2:1.

But “when all is said and done” it is up to your decision and choice of color, shape and cut.
Also be aware that what you love may not be cherished in the same way by another person, and that is the way it should be, otherwise it would be a boring world where there did not exist any individualism and everybody had the same clothes, jewelry, cars, houses and so on, terrible!

For more information try GemSelect or Multicolour or Africa Gems

I hope you will find this short info useful.

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