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Colored gemstones
 
Colored stones are far too vast field to cover properly in an article of this purpose and caliber. Their gemological aspects are properly covered in many web sites. What I will try to cover are aspects which are rarely mentioned but very important to know in order to make the right choice at the right price.
First we will try to tackle the classification issue which is a bit outdated and confusing. Colored stones are divided in too major groups: precious and semi precious.
Precious stones are the good old classics: ruby, sapphire and emerald.
The rest of the gemstones are classified as semi precious although some of them
are rarer and sometimes more expensive than the precious ones. To shortlist the vast field of the semiprecious family we will exclude from now, all the members not used in jewelry ,reason being not hard enough to wear and having only collector’s value. Colored gemstones compared to diamonds are very difficult to classify because of the vast variety of types, colors, size, hardness, current demand and marketing efforts among others. To be able to know exactly the price of certain stone one have to be actively dealing with it for long time and have his prices updated monthly. We will try to make things simpler. There are some rules that apply to all colored stones and if we know them we will reduce our chances of making a wrong choice.
First rule: color. This one sounds simple .The brighter, the better.
Color in gemstones is often described using the following three characters:
• Hue is the shade, tint or sensation of a color - your first impression when you first look at the gem. The GIA grading system recognizes 31 hues
• Tone (or value) is the relative lightness or darkness of a Hue and is rated on a scale of 0 (colorless) to 10 (black).
• Saturation is the intensity, strength or purity of a Hue. It is rated on a scale from 1 where cool colors such as blue and green tend to look grayish up to 6 which is described as vivid (almost over colored).
There is a perception that the more intense the color the better the quality.
It is totally wrong! If you compare stones from the same variety, the one of medium intense colour are always the most desirable and expensive ones followed by the lighter ones and in the end the dark. The further the color deviates from the desired medium intensity the cheaper the stone become. This is not difficult to understand. The medium stones reflect light and show the color at its best. They are the prettiest. The light stones reflect even more light but they are pale. Sometimes the intensity of the color defines the gemstone as such. Pale tsavorite is called green grossular garnet, pale emerald is a green beryl and a pale ruby becomes a pink sapphire. The difference in price is huge. Last, the dark stones reflect only very strong light or no light at all and have opaque appearance. Their price is only a fraction of the same size medium stone. Another rule for color is that clean bright colors are usually more desirable and expensive than the mixed or tinted ones. Brown or grey overtone in the color is unwanted and brings the price down.
Second rule: The transparent stones are more (much more) expensive than the translucent or opaque ones.
Clarity is the term usually used to describe how clean and pure a gemstone is using a 10X magnification. Of major importance is how the gemstone looks to the unaided eye. When free of flaws and inclusions to the naked eye, the gem is termed to be "eye clean" in the gemstone industry. Colored Gemstones should be as close to "eye clean" as possible. Many species of colored gemstones simply do not naturally occur without inclusions. Colored Gemstones are not graded to the same strict clarity tolerance levels as diamonds are, but a good rule to remember is, the fewer inclusions or flaws, usually the better the gemstone.
The tolerance of inclusions is different for different type stones. The Emerald is almost never flawless while for Zircon or Topaz is a norm. Heavily included precious stones are cut en cabochon (domed, non faceted shape with relatively flat bottom). Inclusions are undesirable and brig the price down, but there are exceptions, The rare demantiod garnet for example is much more expensive if it has the characteristic “horse tail” inclusions.
Type I colored stones include stones normally have very little or no inclusions. They can include Aquamarine, Topaz and Zircon, among others.
Type II colored stones include stones that often have a few inclusions. They include Corundum, Garnets and Spinel, among others.
Type III colored stones include stones that usually have inclusions. Stones in this category include Emeralds, Spessartine, etc.
Third rule: Carat- One carat diamond is bigger than one carat ruby
A Carat is a metric unit of weight used in the gemstone industry to describe how much a gemstone weighs. A carat is equal to one fifth of a gram.
With many gemstone varieties, the larger stones are significantly rarer than smaller stones of the same quality and consequently more expensive. The specific size, at which a type of gemstone increases significantly in price, varies with availability of that gemstone species in the marketplace.
The carat weight of two gemstones can be the exactly same, yet there physical size can be totally different. For example, a one carat round diamond is around 6.5millimeters in diameter, but a one carat ruby, generally would be a much smaller stone. Ruby is heavier than diamond and it may take a 1.4 carat ruby to match the size of a 1.0 carat diamond.
To match gemstone size, use physical measurements (millimeters is the "standard" unit of the industry) rather than carat weight.
Cut
As with the diamonds, the cut, meaning proportions symmetry and finish, is of extreme importance for the appearance of the colored stone
Proper cutting is what gives a gemstone its life, beauty and brilliance. The cutting is what makes the difference between a mere rock or pebble and a beautiful gemstone. Judging good cutting is relatively very simple even for the novice. When viewing a gemstone, look at the top flat facet (the table) of the stone. A well cut gemstone will be very bright across the entire surface of the gem and look beautiful and alive.
Poorly cut gemstones (too shallow or too deep) are displaying a "window". When you see a group of facets, usually in the center of the stone looking from the table down towards the culet, (the point on the bottom), that does not reflect light back but rather appear transparent ,the stone is said to have a window. Windows tend to weaken the intensity of color and can severely affect brilliance. Almost all gems have transparent facets, depending of the angle they are observed from, but the idea is to keep them to a minimum. The smaller the window the better the appearance.
Rarity
The rarity and popularity of gem stones are two very different issues. Really rare
gemstones are usually not well known due to lack of marketing. No one will spend money, marketing product that is not available. Let us take the very popular and well marketed tanzanite for example. As rare as it is (mined in only one location in the world) it is available in every location in the world and sizes over 5ct. are expensive but easily obtainable. There is a fine balance between rarity and marketing budget. Marketing is closely connected to the demand hence the steady increase in value, but If you are looking for a really rare gemstone that will make you stand our in the crowd you have to look further than the beaten road.
Another issue is the rarity of certain size and color of a particular stone. Ruby
is found in good quantities all over the world but good quality transparent material suitable for faceting is rare and when it come to saturated intense red in sizes over 3ct., very rare.
Another misunderstanding is connected to the common name of gemstones belonging to the same family. The best example is the garnet family, home to gemstones with very different properties, color and price. The well known dark brownish red variety of garnet is the pyrope. This is the picture that comes to mind when we talk about garnet, together with the idea of big size stones on grandma’s broach and very low prices hardly covering the cutting cost.
Some garnets are really rare, beautiful and very expensive. That apply mainly to the green ones, tsavorite and demantoid, although the orange mandarine and some rhodolites are just as beautiful.
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Your host Vasco Kirov
Award winning jewelry designer
and master goldsmith
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