Grading Turquoise Matrix: What Turquoise Patterns are Made of
Turquoise forms under ground over thousands of years. Turquoise forms within what we call the hosting rock or mother stone. Not all the material of the host rock changes to turquoise. This leaves fragments of other types of natural material within the turquoise stones. The turquoise matrix is the term used to describe the remaining host material found in turquoise stones. This material can be a wide range of elements from quartz to metallic pyrite to sandstone, each adding unique qualities to the final stone. The combination of colors of the stone and matrix can form beautiful shapes and patterns. Some are more desirable than others. Clarity is a way of describing the purity of turquoise, independent of the matrix or host material. A grainy or cloudy appearance can indicate imperfections during formation, or specks of the host material.
How the Matrix Influences The Value of Turquoise
The matrix pattern and clarity of the turquoise coloration are factors that a judged. The Turquoise Quality Index (or TQI) is a turquoise pricing system that takes two factors into consideration when determining a stone’s price value: Matrix and Consistency. Generally, the true value of a specific pattern is based on the rarity of that particular pattern. The rarer the pattern, the more valuable the stone. Synthetic stones are always given a 1. Stones that have been artificially engineered never receive higher than a 2. Natural stones are examined more closely. The score for natural stones is 1 + (Matrix Pattern) + (Consistency).
Synthetic = 1
Dyed = 2
Natural = 1 + Matrix Pattern + Consistency
| 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 |
Rare Turquoise Matrix Patterns
Extremely high valuations are given to stones with rare particular patterns, such as spider web, water web or micro web pattern variations. Another rare pattern is the Calico, which is the combination of light golden brown, dark brown or black matrix against turquoise and specks of metallic pyrite. On the complete other end of the spectrum, some collectors value pure turquoise for not having any matrix at all.
This is a gray scale gauge of the most valuable pattern, called the spider web pattern. The picture takes color out of the equation. The image on the far right is an exaggerated version of the pattern and the most valuable.
Pure turquoise no matrix: +4
Little matrix: +1
Good solid matrix, no pattern: +2
Good matrix, premature patterning: +3
Rare patterns: +4
Exaggerated rare patterns: +5
The Spiderweb Pattern
The spiderweb pattern has been generally accepted by most in the turquoise industry as the most valuable pattern. It is rare to find in nature and is said to have the best structure. This is why the exaggerated versions of this pattern score this highest possible score of a +5 of the matrix pattern scale. This is important to know because these patterns are prone to be replicated by engineered imitations.
Turquoise from Carico Lake Turquoise mine progressively forming the spiderweb pattern. The stones score from +1 to +5 on the TQI scale from left to right.
Variations of the Spiderweb pattern
There are several variations of this pattern that are highly sought after by collectors. The exaggerated microweb is probably the most sought after turquoise matrix pattern. This pattern features the web that is much smaller and condensed, compared to the classical web. The megaweb pattern is another highly prized exaggerated spiderweb version, the black webbing is much thicker than the classical spederweb. Due to their rarity, both of these patterns score a +5 on the TQI scale. The final variation is the so called waterweb, The turquoise in the web appears to be floating over the matrix like water over a riverbed in 3 dimensions. This pattern scores similar to the classical spiderweb designs.
The Calico Pattern
The Calico pattern consists of layers of three or more colors from three different elements. The pattern is formed from a set of natural turquoise blue, a black or brown mother stone matrix and a metallic element such as pyrite. The pattern gets its name from the fur patterns on a calico cat. It is not usually as valuable as the spiderweb pattern though it is rare to find large enough quantities of pyrite and quality turquoise on one stone. The most concentrated forms of this get a +4 on the pattern scale.
Turquoise expressing the calico pattern. The stones score from +1 to +4 on the TQI scale from left to right.
Matrix Free Pure Turquoise
Many western collectors prize their unique matrix patterns, however, the value of pure turquoise (untouched by matrix) has been a bread winner throughout history. It is very rare to have turquoise form completely free of matrix, and the stones that are found this way are extremely small. As an exception in the matrix pattern TQI scale, stones that are are pure turquoise without any matrix receive a +4
Grading Turquoise Clarity
Turquoise Clarity refers to the cloudiness that is visible on the stone’s surface. Cloudiness appears as spotty or grainy color imperfections within the natural color. This not only gives an undesirable appearance but often causes weaknesses in the stone’s structure. The fewer imperfections, the better the clarity, and the more valuable the stone. A stone’s clarity is easy to measure for translucent gemstones such as diamonds; but with opaque stones like turquoise, it is a harder task. Stones get a +1 to +3, depending on the density of the cloudiness. Flawless stones receive a +4.
You may need some kind of tool to magnify the stone so your eye can see how clear the clarity of the stone really is. The images were taken with a macroscopic lens. We can argue that the last two rows have good clarity.
Examples of Grading Turquoise Matrix
This is an amazing natural blue turquoise stone ring centered with a lovely calico pattern. The pattern is the highlight however it is mostly pyrite and turquoise with a little black matrix which gives it that third color giving it the actual calico pattern. It receives a +3 for the pattern for this reason. The pyrite might score it more points in other TQI categories such as composition. The stone clarity is nice but a few areas such as the lighter blue just under the pyrite cluster appears to have some graininess. It using a magnifying glass this is more apparent and causes the stone to score a + 3 for clarity. The total pattern score is 1 + 3 + 3 = 7
This is a natural blue turquoise stone. It could score decently in other TQI categories however it is lacking in the quality of its matrix. The matrix is very scanty and has no patterns, it only receives a +1 for the pattern. The stones clarity is also a little weak, these are also of graininess that can be seen without any magnification. It is not completely grainy so it receives a +2 for clarity. The stone in total scores 1 + 1 + 2 = 4
This is a Chinese medium blue-green turquoise stone with a premature spiderweb pattern or a basic spiderweb. This is a great example of how stabilization saved the appearance of this stone. There is obvious webbing but it is not quite to the quality that we consider the classic spiderweb. Its pattern still scores a +3 for approaching this rare pattern. The stones clarity is ok but there is some obvious graininess when using a magnifying glass around the areas of harsh color transitions that may have been caused by a stabilizing technique. The stabilizing technique probably also increases its clarity. It scores a +3 for this area. The total score is 1 + 3 + 3 = 7
This is a natural stone from the Sleeping Beauty Turquoise mine. This mine know knowns for its limited matrix and high clarity. As you can see it is almost completely turquoise except for a small island of turquoise matrix near the bottom. If it didn’t have this matrix it would have receives a +4 for being pure. This stone receives a +1 for showing a common pattern. On the other hand, the clarity is great! There is no graininess to be seen, so it receives a +4 for clarity. In total the stone scores a 1 + 1 + 4 = 6
