Turquoise has been a precious gem material for thousands of years in many continents. It is used in ancient egyptian, persian and native american jewelry. The properties of turquoise that determine its value are its color, hardness, inclusions, rarity, treatments, polish/finish and size. Unlike most gem materials, turquoise varies significantly in terms of its hardness – so when new “types” are found, their hardness is one of the properties that determines how valuable they are.
Traditionally, the finest turquoise is considered to come from Iran. However, within the last 200 years, a turquoise culture and connoisseur-ship has erupted in the American Southwest. This region values turquoise eith attractive matrix that comes from mines that have been closed.
The valuation of turquoise is therefore, somewhat subjective and varies between regions.
The Most Valuable Turquoise:
The most valuable turquoise are large, natural (untreated) perfectly polished, hard peices of strong “robin’s egg” blue with no inclusions or containing even, attractive inclusions characteristic of an old non-producing mine.
|
|
|
|
|
| Lowest Value: This turquoise is small, pale and reconstituted. A peice of turquoise like this is worth less than $20. | Low Value: This turquoise peice is valuable for its large size and because it is natural. However, its color has unattractive brown and yellow tones and the “matrix” of inclusions is uneven | High Value: This turquoise cabochon is valuable for its bright blue color. Though it does contain inclusions, they are in a more orderly “pattern” and can be considered attractive. It is also quite large and has a trong polish. | Highest Value: Here is a perfect carved peice of natural turquoise. It’s color is bright and attractive, it is free of inclusions, untreated, and hard enough to hold a strong polish. A set of two of these carvings set in cufflinks sold at a Christie’s auction for $7000. |
Color
The ideal color of turquoise is a “robin’s egg blue” or strong sky blue. Colors that are pale, whitish, greenish or yellowish are generally less valuable. Natural turquoise tends to become green over time due to dehydration.
|
|
|
|
|
| Lowest Value: This turquoise peice contains unattractive and low-value colors of brown and pale yellowish green. | Low Value: The pale greenish color of this turquoise is not considered valuable in the middle east and Europe, but it is considered the most valuable in the Far East, namely, Tibet and China. | High Value: This is a very nice color of turquoise: pale sky blue. If it were brighter, it would be even more valuable still. | Highest Value: Turquoise this color is typically the most expensive. It is intense: almost electric. It is only of the highest value, however, when it is natural. |
Inclusions
Turquoise forms over millions of years when water moves through the earth, leaving deposits between other minerals. Turquoise stones often contains these other minerals inside them. The turquoise and other minerals “dance” together in the stone, creating a pattern that is one of a kind. Unlike most characteristics of most gemstones, the valuing of turquoise according to its inclusions is fairly unstandardized and subjctive. Collectors and connoisseurs of turquoise often develop a preference for a particular “look” -and the turquoise stone sthat have that look then become the most valuable in the eyes of that collector.
However, there are some very basic guidelines to use help you get a good deal. No inclusions or inclusions with a regular, or “spiderweb” pattern tend to me more valuable than peices with irregular inclusions. Also, inclusions are often used to identify which mine a piece of turquoise comes from, and therefore increase or decrase its value according to the “prestige” of that mine.
|
|
|
|
|
| Lowest Value: This turquoise cabochon is not necessarily helped by it’s matrix or “inclusions”. They are irregular, and not especially beautiful, except to a collector of this kind of turquoise. | Mid Value: This piece of turquoise has lovely “spiderweb” veins that are farily regular and most people would consider attractive. | High Value: This turquoise has no inclusions. It is natural Persian turquoise ad it is very rare. Turquoise of this quality is universally recognized as quality. | Highest Value: The inclusions on this peice of turquoise make it exceptionally valuable for 2 reasons. They are regular and attractive. They are also characteristic of the mine the stone comes from called “lander” which no longer operates. Such a large piece could be worth thousands. |
The Finish of the Turquoise Gem
Unlike most gems, the physical properties of turquoise vary from stone to stone. Important factors like luster, hardness and density which are standard in many minerals are represented in wide ranges in turquoise. These factors affect how shiny and how durable a turquoise stone can be. The most desirable turquoise stones have high luster (very shiny) and are quite dense and hard (means they will polish nicely and not scratch easily).
The workmanship of the stone will also affect it’s vale: how nicely it has been cut and polished. The most valuable turquoise stones will not have chips or rough spots.
|
|
|
|
|
| Chalky: |
This turquoise from China has a chalky, rough texture and does not hold a polish.Nugget:
These turquoise nuggets seem to have a nice luster. However, because they have not been cut into cabochons, their value is less than similar stones that have been through more workmanship.Poorly Polished
Here is a turquoise that HAS been cut into a cabochon. However, we can see that there are pits and bumbs that have not been properly polished away. The cutter chose to do this to save as much of the material as possible.Perfect
Here we see a perfectly finished quality turquoise cabochon. It is shiny (good luster) and is also cut and polished nicely which shows good workmanship and suggests strong hardness.
Size
As with all gemstones, the bigger the piece of turquoise, the more valuable it is. The price diference is compunded by two factors: 1. There is more material, so it is worth more and 2. Large pieces are harder to find (rarer) than small pieces. This means that if you have 2 cabochons of the same qualit, each of them 10 carats, their combined value will be less than 1 20 carat cabochon of the same quality of turquoise.
Origin
Especially in the southwest of the USA, the value of a peice of turquoise is affected by the prestige of the mine it comes from- its reputation for producing quality pieces and whether or not the mine is still producing.
Effectively,if two pieces of identical turquoise (doesn’t of course exist, but hypothetically) are from two difrent mines, the one from the famous mine no longer in production will be more valuable.
There are hundreds of mines all across the world. Here are some examples:
|
|
|
|
|
| Kingman: This mine is currently producing massive amounts of stabilized turquoise. It is not among the most valuable. | Bisbee: This turquoise is very highly praised and very rare. It comes from a mine in Arizona that is no longer operating. | Sleeping Beauty: This turquoise is famous for it’s bright blue color and it’s relative freedom from inclusions. | Lander: Turquoise from this mine is very valuable. It is well known for spectacular pieces and it is no longer in production. |
|
|
|
|
|
| Turquoise Mountain: This turquoise is hard to find. It is from an Arizona mine that no longer operates. | Cerrillos: From one of the oldest mines in the southwest, this New Mexican turquoise is found at the base of a volcano, making it exceptionally colorful. | China Mountain: This turquoise comes from China. It is a good bargain because of its high quality yet low price because it’s not rare. | Blue Gem: This is a very nice material that comes from a Nevada mine currently operating. |
Treatments:
Because of the vaue and popularity of turquoise in the last several decades, a myriad of treatments and synthetics have entered the market. In fact, it is harder to find natural turquoise than it is treated or synthetic turquoise. 80% of turquoise has been treated to improve either its color or durability. Treatments are used to make inferior peices of natural turquoise harder and therefore more resistent to wear; durable enough to take a high polish. Treatments are also used to strengthen and enhance the color of paler less valuable turquoise stones.
Impregnated or “stabilized” turquoise: Naturally porous turquoise is sometimes treated by the absorption of resins, epoxies, parafin wax or plastics. This improves its texture and durability. You can tell if a gemstone has been treated this way by poking it with a hot needle. If it smells like plastic, you know it has been treated in this way. You can also tell by scratching it with a knife: treated turquoise has a hardness more like that of plastic, and therefore will scratch, whereas natural turquoise is harder and will not scratch under the knife.
Dyed or “enhanced” turquoise: These turquoise stones have been dyed to improve color. Some of these techniques are very difficult to distinguish from natural turquoise.
Backing: This is a technique often used in Native American turquoise jewelry. Quality natural turquoise is rare and it is often thin or brittle. In order to maximize the stone and to improve it’s durability, the cutter will often afix the turquoise on another stone using epoxy. This “backing” makes a thin peice less like to break and usable in jewelry.
Reconstituted turquoise: small peices of low quality or “scrap” turquoise is crushed into a powder and then mixed with binders (sticky substances) and pressed back together in a solid mass. Turquoise treated in this way is one of the lesser valued types.
Imitation or “block” turquoise:This is not a treatment or form of genuine turquoise, but rather another substance that “pretends” to be turquoise. It is fake turquoise. Substances can include plastic, ceramic, other dyed reconstituted rocks, dyed resinous materials. You can tell the difference between plastics and resins and real turquoise by holding them in your hand for about 7 minutes. The plastic will get warm while the turquoise will not.
|
|
|
|
|
| Plastic Imitation | “Block” turquoise | Dyed Howlite Imitation | Dyed Magnesite Imitation |
|
|
|
|
|
| Reconstituted | Stabilized Turquoise | Natural Turquoise with backing | Natural Turquoise |
