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Facts and figures about Diamonds.

 

Diamonds and Gems:

Diamonds are the hardest of all gemstones and the hardest transparent substance. Natural diamonds are found in Kimberlite or Lamproite pipes produced by volcanic magma millions of years ago. Diamonds are a simple crystalline structure of carbon produced by extremely high pressure and temperature. The melting point of a diamond is 4,000 degree C or about 2.5 times higher than the melting point of steel. Gem quality diamonds are rare; this helps to account for their value. A rough diamond resembles a common pebble; but when properly cut and polished by a skilled diamond cutter, its "fire" or brilliance comes to life. Fire can be a seen as a flash, spark, sparkle, or animation of light and colour caused by the proportioning, angles and positioning of facets that reflect and refract light inside the diamond. Facets must be precisely cut so that light bounces freely inside the diamond, and then exits through the crown or top, directly to the eye of the viewer. The table, top or crown facet is the largest and most important facet on a diamond. It takes from several hours to several months to cut and polish a diamond, depending on the size, shape and style of the final product. During cutting and polishing, a rough diamond will lose approximately 50% of its original weight.

 

More information is also to be found in even more detail throughout this website in other places.
 

 

Diamonds & Gems

What is a gem? A gem is something which has Beauty, Durability, Rarity, and Value.

 

A butterfly's wing has beauty, rarity, and value, but no durability. A fine Opal may have the same colours and beauty. It has rarity and value and is relatively durable (if not abused), so it is considered a gem.

 

Gems can be classified as Organic and Inorganic. Most gemstones are inorganic. Rubies, Sapphires, Topazes, etc., form as crystals of minerals and are inorganic. Some "gem materials", however, are formed organically. Pearls, Coral, Amber, Jet, Ivory, and Shell, are all organic gem materials. We also have some gem materials that were organic, but come to us as mineralized fossils. Ammolite, and Opalized bone are examples of this.

 

It is important to know the difference between Natural, Treated, Synthetic, and Imitation.

 

Natural gems have formed without any help from Man. They may then be treated or untreated. Many natural stones are treated in some way to bring out beauty that nature didn't. Almost all Citrine on the market today was mined as Amethyst and later heated to change it's colour from purple to yellow. Blue Topaz is very rare in nature, but colourless topaz can be irradiated and heated to give it the lovely blue colour we're accustomed to seeing in jewellery. We will cover more on treatments later.

 

Synthetic stones have all the physical, chemical and optical properties of a natural stone, but they have been created by Man. Some people use natural Sapphire, grind it up and grow new crystals (re-crystallize it). They may be tempted to call the resulting stones "natural", but whether the material came from nature or from a laboratory supply house, the resulting stone is man-made and therefore "synthetic".

 

Imitation stones do not have the same properties as the stone they are imitating. They just have the appearance. Rhinestones are made of glass and have none of the distinguishing properties of a Diamond, but they look like fine Diamonds.

 

You have probably heard gemstones referred to as "precious" and "semi-precious". We no longer use those terms because they can be misleading. A very fine Jade may be worth many thousands of dollars. Many Black Opals cost between $1000 to $5000 per carat. A fine red Topaz of several carats may cost $10,000. "Precious" stones (the big four) may cost only a few dollars per carat. Poor quality Diamonds can be bought for a few hundred dollars per carat and Rubies, Sapphires and Emeralds may go for as little as two or three dollars per carat.....hardly what we would call "precious".

 

When judging the value of a stone you will need to judge the famous "4 C's". They are Colour, Clarity, Cut, and Carat (weight). The 4 C's are basically a way of quantifying BEAUTY. Durability and rarity are also important, but all things being equal, beauty will make the difference between high and low value in a gem.

 

If you compare two Sapphires side by side and they are alike in all but colour, the more beautiful colour will cost more. If you compare two Topazes side by side, the more intense colour will be more valuable.

 

People often ask: "Is the darker colour more valuable than the lighter colour?" Here the proper way to find the answer is to consider beauty. A stone that is too light will not be very attractive. A stone that is too dark will be dull and lifeless. The stone with an intense colour and lots of flashes of light will be eye catching and very attractive. That is the stone to look for.

 

Back to the 4 C's. If you have two stones of very lovely intense colour, the stone with the most clarity will be the most beautiful.

 

Between two stones with fantastic colour and flawless clarity, the better cut of the two will show itself to best advantage. A poorly cut flawless diamond will look like a piece of cheap glass. Proper cutting makes the best use of the optical properties of a stone. That is where the sparkle and brilliance come from.

 

Finally, all things being equal, the larger stone will be worth more. Some stones such as Amethyst and Citrine are easy to find in large sizes so their "per carat" price changes very little with size. Many stones, however, are rare in larger sizes and the per carat price skyrockets in larger stones. Alexandrite is a good example. Small gems of under a carat can be expensive, but when they get over a carat the price jumps even higher.

 

Keep in mind that stones form in nature, kind of like in your backyard in the dirt. Nature isn't exactly a cleanly swept laboratory so gems usually have various imperfections or "inclusions" in them. When a gem crystal is found, it may be easy to find a small area of perfection in it to cut into a small gem. A large piece of perfection is much more rare and so will be much more valuable.

 

 

Colour

We will begin by discussing colour in Diamonds. Diamonds come in all colours. The most expensive stones in the world are red Diamonds. A 1 carat red Diamond sold at auction for approximately one million dollars!

 

Diamonds are usually thought of as being white, and the less valuable ones as off-white. When a Diamond has enough colour to be a "coloured" Diamond it is known as a "fancy".

 

First we'll talk about white and off-white Diamonds. The Gemmological Institute of America has the most widely accepted grading system for Diamonds. When they invented their system they decided that since A, B, and C, had already been widely used (and misused) for many things they would avoid those letters and start with D.

 

Thus it is that a completely colourless (white) Diamond is graded as a "D". Loose Diamonds up to G will usually appear colourless. When they are set in yellow gold you won't be able to judge colour. A stone with an easily distinguished yellow tinge will be completely masked by yellow gold.

 

D, E, and F stones are considered colourless. G, H, and I are excellent and it really takes an expert to notice that they have any colour to them. J, K, and L are noticeable but accepted by most people. M through Z are obvious. After Z begin the "fancy" yellow Diamonds, etc. From D to Z the value goes down. After Z the value may go up again. That depends on several factors. Rarity is one important factor.

 

Red is the rarest colour of Diamond. It is also attractive, so it's the most valuable. Pink is next in line; it's really just a light red. Blues, greens and yellows are very pretty in the strong tones. An important thing to mention here is the fact that Diamonds can be irradiated to achieve colour. Very often, off colour Diamonds are subjected to either neutron or electron bombardment to give them a fancy colour. Irradiated Diamonds are usually a brighter and stronger colour than natural fancies. The process is permanent and beautiful but irradiated Diamonds are much less expensive.

 

You have probably heard the term "blue-white" used in describing Diamonds. True blue-white Diamonds are very rare, and the term is no longer used by good jewellers. A blue white Diamond is one that is very white (D colour) but in ultraviolet light (such as sunlight contains) it has a slight bluish fluorescence. The term became very much abused some years ago by unscrupulous dealers. Some dealers were even calling K and L colour stones blue-whites!

 

Gems other than Diamonds are usually referred to as "coloured stones". Many types of stones that we are used to thinking of as being a particular colour, actually come in many colours. Diamonds and Sapphires come in all colours. Sapphires (the mineral corundum) are called Rubies when they are red. Garnets are commonly red and brownish red, but they also come in orange, pink, purple, and green. Fine green Garnets rival fine Emeralds and are much more durable.

 

Topazes are well known in the yellow colour known as "Precious" Topaz, but they also come in champagne, sherry, blue (from very light to quite dark), pink (known as imperial Topaz), and all the way to cherry red (rare and very expensive). Citrine and Amethyst are two different colours of Quartz, which also comes in light to dark Smokey colour, often mistakenly called Smokey Topaz. The mineral Beryl comes in several colours. Green Beryl with the impurity chromium is called Emerald. With iron as a colour causing impurity it will be blue and is called Aquamarine. Pink is called Morganite, yellow is called Heliodor, and colourless is called Goshenite. Spinel, Zircon, and Tourmaline all come in many colours too.

 

 

Clarity

The next of the four C's is clarity. It is normal for stones to have small inclusions in them. Less inclusions mean more value. The GIA definition of an internally flawless Diamond is one in which "an expert, with a ten power magnification, can not find any inclusions". Inevitably that same stone may show many inclusions if the magnification is stepped up enough.

 

Between two equal stones, the one with less inclusions will be more attractive....that is where the value lies.

 

Most faceted stones are cut so that light will enter, reflect, and come back out toward the eye, thus giving flash and brilliance. Any inclusions in the stone will block that light and prevent it from coming back out. Too many inclusions will make a stone cloudy or dead looking. In Emeralds inclusions are so frequent that they have been given the name "garden" and they are viewed as normal. Flawless Emeralds are available but they are more rare than other flawless stones and correspondingly more expensive.

 

There are many kinds of inclusions. In Diamonds, dark inclusions are usually called "carbon" spots, but actually the only part that is not carbon is the inclusion. The diamond is made of carbon and the inclusion is a foreign particle contained in it. Garnet, Peridot, Pyrite, Hematite, and Spinel are frequently found in diamonds. The inclusion may look black, but it rarely is actually black and it's not carbon. There are also white inclusions and they are usually harder to spot. Being hard to see, they don't detract from the stones value as much as an obvious dark inclusion.

 

When looking for inclusions in a stone, with or without magnification, turn it in various directions and rock it slowly back and forth, looking for any specks or spots, lines or "feathers" inside the stone. Don't let dirt or lint on the surface fool you. It's important to get the stone as clean as possible or you are wasting your time. Whenever possible, look at the stone from the bottom or "pavilion". Especially in the case of Diamonds, it is much easier to see inclusions from the bottom. A well cut Diamond is reflecting a lot of light out the front and looking for inclusions is a little bit like trying to read the writing on a car headlight from the front while it's on.

 

Here is an approximation of the Gemmological Institute of America clarity grading criteria:

Using ten power magnification the inclusions seen are:

 

VVS1 Minute "Extremely difficult to see"
VVS2   "Very difficult to see"
VS1 Minor "Difficult to see"
VS2   "Somewhat easy to see"
SI1 Noticeable "Easy to see"
SI2   "Very easy to see"
I1 Obvious "Beauty or Durability somewhat affected"
I2  

"Beauty or Durability seriously affected"

I3 Prominent

"Beauty and Durability seriously affected"

 

 

Cut

Our third C is cut. We are going to deal with faceted stones, that is, stones cut with flat faces or facets. If a stone is cut properly, light will enter it, reflect or bounce around, and come back out to be seen and enjoyed. You may notice that if you hold a piece of glass and tilt it, at a certain point you can't see through it any more. You begin to see a reflection. Inside a gemstone, the angle has to be right for that light to reflect also. If the stone is not cut properly, light will pass through instead of reflecting back. That results in a transparent, washed out looking stone. We call that "windowing".

 

In stones with high refractive indices, light is split into it separate colours, like in a prism. That is why a Diamond sparkles with all the colours of a rainbow. Again the stone must be cut properly to take advantage of it's light splitting properties.

 

When trying to judge a stone, you will get a big clue about it's quality from how well it is cut. High quality material is usually given the respect of good cutting. Poor material is not usually considered worth the time, trouble, and extra expense of careful cutting. Synthetics may be exceptions to this because they are cheap and are often cut on machines without worrying about loss of weight in cutting.

 

When viewing a round Diamond, the symmetry of the cut is a big clue to its quality. the table (the flat top of the stone) should be exactly the shape of a stop sign. If it is lopsided or uneven, it is not well cut, and may not be a very good stone. Small parallel grooves on the facets come from polishing the stone in too much of a hurry and are called "fast polish checks". Another big clue. If you hold the stone in such a way as to see light reflected off of the facet, you can usually see its symmetry and polish even without magnification.

 

Look at the overall symmetry of the stone. Is a round stone actually round or a little out of round? Is a square stone even on all sides? Are the sides parallel? Is the table centred at the top?

 

The main cuts you will see are Round, Oval, Emerald cut, Marquise or Navette, Pear shape or Teardrop, and Baguette (straight and tapered).

 

Different cuts have different values, varying with the type of stone. Marquise cut Diamonds are the most expensive for two reasons. There is a great demand for that cut and the weight lost in cutting is greater than in other cuts. The least expensive cut in large Sapphires is the oval cut. A three carat round Sapphire is very hard to find but a three carat oval is not.

 

 

ROUND BRILLIANT SINGLE CUT ANTIQUE CUSHION CUT

MARQUISE PEAR OR TEARDROP (PENDELOQUE) OVAL

EMERALD CUT (OCTAGON)

BAGUETTE

TAPERED BAGUETTE

PRINCESS CUT

RADIANT CUT

SQUARE CUT

TRIANGLE TRIELLE TRILLIANT
OLD MINE CUT

 

Some other cut names and variations:

Radiant Trillion Princess Portuguese

Quadrillion Trilliant Kite Trapezoid

Quadrilliant Half Moon Hexagon 144 cut

Bagillion Rose cut Dutch Rose

 


CABOCHON CUTS are rounded, most often have flat bottoms and don't have facets. Opals, and Tigereyes are usually cut cabochon style. Cabochons are also cut in the same basic shapes and would be called: round cabochon, square cabochon, oval cabochon, etc.

 

 

 

 

Carat (Weight)

The last of our Four C's is carat weight. One carat consists of 100 points just as there are 100 cents in a dollar. That means that a 25 point stone will be a quarter carat, a 66 point stone will be two thirds of a carat, etc. 5 carats equal one gram, so a one carat stone weighs one fifth of a gram (.20 grams). Don't get confused between Karat and Carat. Karat refers to the purity of gold and we will cover that later.

 

Carat weight affects the value of a stone in three ways. First, obviously a two carat stone (all things being equal) will cost more than a one carat stone simply because there is twice as much of it. Second, when cutting the rough stone, it will always be easier to find a small piece of relative perfection than a large piece. Third, some stones are rarely found in sizes over a few carats, so, while small ones may not be too expensive, slightly larger ones may suddenly be very expensive.

 

Citrine, Amethyst, Smokey Quartz, and Blue Topaz are frequently found as very large stones and the per carat price is usually the same even in the larger sizes. The same quality of Peridot may be $10 to $15 per carat in a small size and $60 to $100 per carat in a three or four carat size.

 

 

Weight Formulas

We will examine some very useful formulas for estimating the weights of Diamonds. You may want to use these if you'd like to estimate the weight of a mounted stone or maybe a loose stone if you don't have a scale.

 

Round

Estimated weight = average diameter squared x depth x .0061

 

Oval

Estimated weight = average diameter squared x depth x .0062

 

Emerald Cut

Estimated weight = length x width x depth x adjustment factor

Length-to-width ratio Adjustment factor

Length-to-width ratio = length divided by width

1.00:1.00   0.0080

1.50:1.00   0.0092

2.00:1.00   0.0100

2.50:1.00   0.0106

 

 

Marquise

Estimated weight = length x width x depth x adjustment factor

Length-to-width ratio Adjustment factor

Length-to-width ratio = length divided by width

1.50:1.00 0.00565

2.00:1.00 0.00580

2.50:1.00 0.00585

3.00:1.00 0.00595

 


Pear Shape

Estimated weight = length x width x depth x adjustment factor

Length-to-width ratio Adjustment factor

Length-to-width ratio = length divided by width

1.25:1.00 0.00615

1.50:1.00 0.00600

1.66:1.00 0.00590

2.00:1.00 0.00575

 

Diamond Diameters and Corresponding Weights (These are approximate)

Size (mm) Weight (ct)
1.15 .005ct
1.35 .01
1.55 .02
1.90 .03
2.10 .04
2.30 .05
2.70 .06
2.90 .07
3.10 .10
3.50 .15
4.10 .23
4.50 .33
5.13 .50
5.88 .75
6.50 1.00
6.90 1.25
7.40 1.50
8.20 2.00

 

 

 

Gem Treatments & Enhancements

Most of the gems that you see on the market today have been treated or enhanced in some way. Some people are disappointed to learn this. The positive side is that because of these treatments and enhancements, you can own and enjoy a fine gem without having to be extremely wealthy or the equivalent of royalty.

  • Here's a list of Treatments:

  • Heat

  • Radiation

  • Drilling (and Laser)

  • Oiling

  • Sealing

  • Dyeing

  • Bleaching

  • Painting or Coating

  • Foil-Backing

  • Fracture Filling

 

White Topaz is irradiated and then heated to create Blue Topaz. Diamonds can have dark inclusions removed by laser drilling. A very thin hole is drilled down to the inclusion and acid is introduced to dissolve it. Now the same "inclusion" is there but it is now a clear vacant space instead of a dark (and easily seen) spot. The Diamond is now a bit more attractive and thus easier to sell. Emeralds have been oiled since ancient times. Different kinds of oils that have the same or almost the same refractive index are used to fill cracks and fractures. The result is that the cracks are now invisible, thus making for a much more attractive gem. If coloured oils are used then it is also dyeing. Many gems can be dyed as long as they are either porous or cracked. Pearls are often bleached. Coral is too. The backs of gems can be painted to make them seem to be of strong, more intense colour than they really are. Foil backing is the mirror backing that makes rhinestones so brilliant. Fracture filling (also called the Yehuda process or clarity enhancement) makes cracks and fractures invisible like in oiling except that the process is more durable. This is used in Diamonds and is becoming common in Emeralds too. In Diamonds the fracture fillers use very high heat and pressure to force a special glass-like filler into the cracks that reach the surface. In Emeralds a two part clear epoxy called Opticon can be used.


Gem treatments are wonderful when they are used to enhance the beauty of a gem. FULL DISCLOSURE is the LAW. These treatments can also be misused to sell less expensive gems as their more expensive cousins. Make sure you go to a jeweller or gem dealer who keeps up with new developments and can tell the difference.

 


Misnomers

There are a number of incorrect names for gems and they can be confusing and misleading. Here are a few of the more common ones, and the actual stone referred to:

 

Misnomer Correct Name
Arkansas Diamond Quartz crystal
Herkimer Diamond Quartz crystal
Balas Ruby Garnet
Colorado Ruby Garnet
Montana Ruby Garnet
Cape Ruby Garnet
Water Sapphire Iolite
Poor Manís Tanzanite Iolite
Smoky Topaz Smoky Quartz
Indian Jade Aventurine
Manchurian Jade Soapstone
Nassau Pearl Conch Pearl

 

 

Hardness

An important property of gemstones is their hardness. Diamond is the hardest and is rated a hardness of ten on the "Mohs" scale. A man named Mohs rated different gem materials according to their hardness relative to one another. It's important to remember that hardness and toughness are not the same. Diamond is the hardest, but Jade is the toughest!


Hardness is the measure of how easily something can be scratched and on the Mohs scale any material with a lower number can be scratched by any material with a higher number.


Here are the results of Mohs original research:

 

Mohs Hardness Scale

Hardness Gemstone
1 Talc
2 Gypsum
3 Calcite
4 Fluorspar
5 Apatite
6 Feldspar
7 Quartz
8 Topaz
9 Corundum (Sapphire & Ruby)
10 Diamond


This scale is not linear. As it happens, Diamond is actually about 20 times harder than Sapphire. A fingernail is about 2.5 and a steel file is about 6. Glass is 5 so not only will a Diamond scratch glass, so will most things. Opal at 5.5 to 6.5 will scratch glass and of course C.Z. (Cubic Zirconia) at 8 to 8.5 will scratch it too!

 

 

 

Crystals and Healing

Here are a few beliefs about what healing powers area associated with certain crystals.

 

Amethyst: Acne, adenoids, alcoholism (and/or getting drunk), cankers, eczema and gum ailments.

Azurite: Asthma (and other respiratory ailments) and tonsillitis.

Cerussite: Abscesses, conjunctivitis & other eye ailments, headaches, emotional stress, and hyperactivity.

Cinnabar: Bladder ailments, back pain, appendicitis, leg circulation and hemorrhoids. (WARNING! Cinnabar contains mercury! I donít recommend handling it and especially donít heat it, boil it or eat or drink anything that has come in contact with it!)

Malachite: Bronchitis, diabetes, heart ailments, flu and pleurisy.

Pyrite: Circulatory problems, liver and kidney aliments, dry skin, gastritis, and flatulence.

 

Australian Aborigines, among other indigenous populations, also still use Crystals for medicine. Their favourites are Multi-Colour Crystals, as they believe that they hold the energy of the Rainbow Serpent, acting as a bridge between the spirit and physical worlds.

 

 

 

 

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