Turquoise Value, How Much is Turquoise Worth?
What is the value of your turquoise stone? How much a turquoise stone is worth is a common question among turquoise collectors. The price of turquoise stones normally range from $1 to $10 per carat but can range from $0.05 to $1000 per carat depending on the quality. The difference between quality turquoise and cheaper stones can be a little confusing. There are many factors in play that determine a stone’s price, some are subjective and others tend to change over time. The weight of the stone and the Turquoise Quality Index can help us determine how much a stone is really worth.
Turquoise Price = Weight (Carat) X Turquoise Quality Price/Carat Index (TQI)
Turquoise is weighed in carats, where 5 carats equals 1 gram. The heavier the stone, the more valuable it is. It is common to see turquoise priced per carat when it is for sale. So the first step is to weigh the stone, and then figure out what the price is per carat. This price can range from $0.05 to $500 per carat, depending on the stone.
Turquoise Quality Index
The Turquoise Quality Index (TQI) is a measurement of the quality of the turquoise stone. The TQI is a number on a scale between 8 and 100. The higher the TQI number, the better quality the turquoise, the higher the grade and the more valuable the stone. High numbers are rare; less that 1% of turquoise on the market score a 90 or better.
|Turquoise Quality Index|
|TQI Score||Grade||Market Grade %||Price per Carat|
|90-100||AAAA||Superior||less than 1%||$50-$1000|
How to Find TQI
The TQI scoring system is a great way to get a quick estimate. There are two major components that can be evaluated that contribute the true turquoise value. These are the stone’s physical structure and the stone’s rarity. These components are broken down into 8 indicators and weighted according to importance. Determining the TQI is a process of scoring these 8 indicators. Most of these indicators are widely agreed upon; however color, clarity, and stone pattern have been a subject of dispute. It may be hard to get an exact number because of the subjectiveness of these qualities. Also, the availability of turquoise tends to fluctuate respective the production levels of operating mines. This is only a guide to make evaluating the price of turquoise easier. There is usually a slight deviation depending of the person scoring the TQI. For better accuracy please consult with a turquoise expert.
Turquoise is a beautiful, hard, opaque, triclinic cryptocrystalline stone found in shades of green and blue. Chemically, it is a hydrated aluminum copper phosphate. In an arid environment, turquoise forms inside the earth within host rocks (such as limestone and sandstone) under and high temperature and pressure, making it as hard as glass. The combination of different elements in the host rock material can change the appearance and structural integrity. Some turquoise is not formed completely and needs the aid of enhancing agents to make it usable in jewelry. The resulting stone’s physical properties are key indicators that help determine the value of the stone.
Physical structure makes up 55 points : Hardness (20), Enhancement (20), Composition (10), and Cut (5).
|55 points (total)||20||20||10||5|
No two turquoise stones are alike. The fragments and impurities of the host stone that are not transformed into turquoise create a matrix of lovely unique colors and patterns. Synthetic plastic turquoise that has been dyed blue and machine molded can be mass-produced, and has little value. On the other hand, a calcium rich sea shell can form into turquoise if it happened to fossilize near a copper vein in the arid American southwest. While this is extremely rare, this can occur in just the right conditions. The rarities of this origin of turquoise, along with other rare quality indicators, bring tremendous value to our favorite blue stone.
Rarity consists of 45 points: Origin (20), Color Pattern (20) and Contiguous Size (5).
|45 points (total)||20||10||10||5|
Use the following charts as a guide to finding the TQI. Each indicator has a list of characteristics and a point value marked below. (for example, if you have a piece of reconstituted turquoise the hardness it earns 10 points) Add the points together to get the total TQI point value.
Measuring Stone Hardness
Hardness is a measurable quality that indicates how easy a material can be scratched. Naturally the harder the turquoise the more valuable it is. Hardness is measured on a scientific scale called the “Mohs Scale” According to the scale, Turquoise has a similar hardness to glass. A Mohs scratch test can be preformed to determine the exact hardness of a material; however doing so would damage the stone that you are trying to measure. For the purpose determining TQI we don’t recommend damaging your precious stone! Simply use deductive reasoning. If the stone is solid then it is probably in the Mols pre determined turquoise range between 3 and 6. For stones that are obviously lower quality use the chart below(1-5). Brittle natural stones that are usually cloudy or stone that have been poorly stabilized receive (10) Stones that have been professionally stabilized are not allowed to receive more than (15) points even if they have a high hardness. Natural stones that seem dull and feel chalky are most likely under 5 on the hardness scale and receive (10). Rare high hardness natural stones may receive (20) points for hardness. If you cannot tell, then give it a (15).
|Hardness||plastic||chalk||reconstituted||Below 5 on MOHS scale||pro stabilization 5+ on MOHS scale||high natural hardness MOHS scale 5+|
|1 to 20||1||3||5||10||15||20|
Enhanced Turquoise Properties
A stone that has undergone treatment to improve its natural state is considered enhanced. There are varying degrees of enhancement; some are very acceptable, other types play a hand in devaluing the market. Pure natural turquoise is not always ideal and it is generally accepted to have some stabilizing. Synthetic turquoise is the most common and cheapest form of turquoise. It is not valuable, because it is pure plastic (1). Reconstituted turquoise is a mix between plastic and turquoise dust, it often looks ok but has a rubbery plastic feel. It receives (2-5) points depending on the quality. Dyes and resins can be injected into a low quality turquoise stone to help stabilize it, and artificially express color (6-12). Professional stabilizing techniques such as the Zachery process are very acceptable. These techniques often leave the finished material harder and more uniform in color. A small amount of oil or wax can be applied to the surface of the stone to help protect it from harmful elements. This is the least invasive form of enhancement and stones receive (13-19) points. Quality natural stone that have not undergone any type of enhancement except polishing or rolling receive (20) points. Finally it must be noted that raw turquoise chalk, even though it is natural, it is not of a quality than can be usable without any form of enhancement. Raw turquoise chalk only receives (5) points on the TQI scale.
|Enhancement||plastic||reconstituted||heavy stabilization/dyed||pro stabilization waxed/oiled / Zachary process||natural||chalk|
|1 to 20||1||2-5||6-12||13-19||20||5|
Turquoise Stone Composition
The composition of turquoise measures the materials that make up the stone. Turquoise by nature is a very chalky stone and the degree of chalkiness is a good quality indicator. Generally the more grainy or powdery the stone is the lower the quality. Turquoise is always formed on another material. This material is called the host rock. The host rock is a completely different material and has its own qualities that can either increase or decrease the worth of the stone. Plastic is not really turquoise (1), reconstituted turquoise has been mixed with plastics and receives a low score of (2-3). Lesser host rocks can be unstable. Turquoise can sometimes be not formed completely, causing the stone to be structurally weak which makes the stone less valuable these stones require some stabilization to even be usable(4-5). A stone that has a solid stable matrix or has been stabilized would receive (6-7) points. If a stone is professionally stabilized or natural with a completely solid turquoise (no matrix present) or has a solid matrix (8-9) points. This is a widely disputed subject, because in some countries it is highly desired to have a pure turquoise stone. The TQI scale promotes rarity, and other elements in turquoise can be more rare in nature. Turquoise can contain other rare elements (such as pyrite) which gives depth and metallic quality to the appearance of the stone without compromising structural integrity (10).
|Composition||plastic||reconstituted/chalk||required stabilization or unstable host rock/ high calcite and quartz in matrix||stabilization and minor imperfections in matrix||pro stabilization pure natural turquoise/ solid matrix||rare elements in matrix|
|1 to 10||1||2-3||4-5||6-7||8-9||10|
The time and energy needed to process raw stones to make them presentable adds a small value. Raw turquoise stones, also known as rough stones, are stones that have been pulled directly from the earth in its most natural state. In an unprocessed state it can be very hard to judge the true value of the stone. It must first be processed so that the stone can be displayed at its finest. Raw stones have now added value (1). Stones can be rolled and polished, machines can help to create standard size cabochons for mass production jewelry making (2). Stones or can be made into cabochons by machine (3) or can be hand cut and shaped cabs (4). Finally, stones can be sculpted by an artist (5).
|Cut||raw||rolled or cut||standard machine cab||hand shaped cab||hand sculpted design|
|1 to 5||1||2||3||4||5|
The less available the stone, the more valuable it is. For example, turquoise can be plastic and easily produced. Mass production of plastic is not valuable and receives a (1) on the TQI scale. Reconstituted turquoise is made from easily available chalk and receives (3) points. The most common indicator on an individual stone’s availability is the turquoise mine. Different mines produce varying quantities of turquoise; within one mine we can find different grades, colors and patterns. This causes this scale to fluctuate from year to year based on the mine’s production and distribution of the turquoise. Common mines such as the large production Chinese mines (6) and the Kingman mine (12) produce a lot of turquoise. Some smaller or uncommon mines are well known, but don’t produce as much. Good examples here would be Dry Creek and Easter Blue. These mines get (13-17) points. Tiny rare mines such as Lander Blue in Nevada, is said to only have produced a few handfuls of nuggets. This makes the turquoise very rare and the value of the stones increase dramatically. These types of mines are called “hat mines” because the amount of turquoise that comes from the mine can fit in a miner’s hat (18-19). Also, rare specimens from any of the mines fall into this category as well receiving (18-19). Lastly, turquoise has been known to develop in other ways such as on fossilized organic remains. Fossil turquoise and petrified wood turquoise are good examples. This is extremely rare and receives a score of (20).
|Availability||synthetic||chalk or reconstituted||common mine||uncommon mine||rare hat mine or rare specimens||extremely rare|
|1 to 20||1||2-5||6-12||13-17||18-19||20|
Turquoise color is one of the more controversial indications of stone value. The ancient Persians would say that the blue color of a robins egg is the most valuable; some modern collectors say the green colors are more valuable. Regardless of the color, clarity is an important indicator of stone value. Rarity, consistency, and contrast of the color are more important factors because color preference are very subjective. This means the hue of the color is not being judged as much as its purity and clear expression. Synthetic turquoise is always a (1) as the color can be controlled, this includes the synthetic color of reconstituted turquoise. Artificially dyed stones received a (2) depending on the consistency of color. Natural stones of very cloudy, dull or rubbery colors with harsh transitions between color shades and matrix get receive (3-5) points. It needs to be noted that cloudy is not the same as white or lighter shades of blue but more a paling or graininess of the natural color. Natural stones that feel limited in the true color expression and may have a grainy clarity (6-7). Stones with consistently darker colors, sharp clarity and rich colors that may have a slight inconsistency (8-9). Finally rich consistent natural colors with consistently sharp clarity receive (10) points.
|Color||synthetic||artificially dyed||dull, cloudy/harsh transitions||limited expression of color, imperfections in color transitions||Rich color, smooth color transitions||Rich color, smooth color transitions|
|1 to 20||1||2||3-5||6-7||8-9||10|
Pattern is also a controversial indication of stone value. In Persia, a pure turquoise stone free from any matrix is the most valuable. Contradicting American collectors feel that the variation of spiderweb matrix patterns is the most valuable . Clarity simply means to be clear or have good contrast. The less dull, cloudy and blurry a stone is, the more valuable it becomes. Rarity is the focus of the TQI scale. Synthetic turquoise is always a (1). Engineered patterns of reconstituted turquoise (2-3) depending on the complexity. Sparse matrix with no apparent pattern (4-5) points. Consistent matrix with little patterning or pre rare patterning (6-7). Rare patterns such as spider web, face stone, calico or pure matrix free turquoise receive (8-9). Finally, natural stones with over exaggerated rare patterns receive (10) points. It should be noted that pure matrix free turquoise cannot be over exaggerated.
|Matrix||synthetic||artificially dyed||no pattern, Cloudy clarity||common pattern, grainy clarity||rare patterns, flawless clarity||rare patterns, flawless clarity|
|1 to 20||1||2||3-5||6-7||8-9||10|
Size That Matters
This is a simple quality that is easy to measure and understand. Even though a very large piece of turquoise might weigh the same as several small pieces, it is usually worth slightly more per carat. This is because it is harder to find large contiguous pieces in nature than small pieces. Again, it is a very small factor and does not usually cause a dramatic change in price. A piece smaller that ¼” at its widest point receives (1) points; between ¼” and 1” (2) points, 1” to 2” (3), 2” to 4” (4). Finally, any stone longer than 4” at its widest measurable point (5).
|Contiguous size||smaller than 1/4″||1/4″ to 1″||1″ to 2″||2″ to 4″||4″ +|
|1 to 5||1||2||3||4||5|
Turquoise Value TQI Price per Carat
After you have a total TQI points compare it to the chart below to get the price per carat.
Fritsch, Emmanuel. McClure, Shane. Ostrooumov, Mikhail. Andres, Yves. Koivula, John. Kammerling, Robert. The identification of Zachery treated Turquoise 1999. Website pdf : http://image1.fmgstatic.com/pdf/The-Identification-of-Zachery-Treated-Turquoise.pdf
Mohs Hardness Scale, A rapid hardness test for field and classroom use. website :http://geology.com/minerals/mohs-hardness-scale.shtml
Smith, Natalie. How to shape Turquoise Nuggets. Website http://www.ehow.com/how_8038446_shape-turquoise-nuggets.html