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
From the T.Skies gallery: browse our turquoise jewelry collection.
From the Library: Pogue, The Turquois (1915)
1915 primary source. Anything described as current here describes 1915, not today.
Pogue (1915) defined the term:
“Many cut stones, however, both by chance and design, show more or less of the accompanying material, which is usually yellow to reddish limonite, quartz (colorless or iron stained), or vein matter (mainly colored by iron and perhaps other metallic oxides). A specimen containing an appreciable amount of such associated material is called turquois matrix.”
— Pogue (1915), p. 23
As of 1915, Pogue reported the market's preference:
“The most valuable stones are those of the approved tint that contain no inclusions of foreign matter.”
— Pogue (1915), p. 23
Pogue (1915) also noted for anyone judging rough:
“The polishing that the turquois undergoes before being worn strengthens the color and color contrasts, a fact to be borne in mind in selecting rough material for cutting and polishing.”
— Pogue (1915), p. 23
Among the features Pogue (1915) found at the most important deposits:
“The turquois is invariably associated with limonite and copper carbonates —minerals not formed below the zone of oxidation.”
— Pogue (1915), p. 63
He also noted, in 1915:
“The turquois is generally associated with more or less kaolin, a substance usually resulting from the weathering of alkalic feldspars.”
— Pogue (1915), p. 63
On pyrite, Pogue (1915) observed:
“Pyrite and copper sulphides are usually present below the turquois deposits.”
— Pogue (1915), p. 64
Writing in 1915, Pogue described the host rock at a Nevada mine named for its dark matrix:
“At the Smith Black Matrix mine (Nevada) the turquois occurs in a jasperoid beneath a rhyolite flow now eroded away.”
— Pogue (1915), p. 66
Pogue (1915, p. 131) divided the stones of the trade into pure turquois, free of foreign matter, and turquois matrix, in which the turquoise is cut together with attached country rock, quartz, limonite or other impurities.
On the value of matrix at the time, Pogue wrote in 1915:
“Very attractive patterns and contrasts are often yielded by matrix, although it never commands the price of the pure turquois. Much material unfitted for pure gems is cut into matrix.”
— Pogue (1915), p. 131
The 1915 name for what is now called spiderweb, as Pogue defined it:
“Cobweb matrix is a term used to designate a blue ground with markings of cobweb pattern (see frontispiece, Fig. 5).”
— Pogue (1915), p. 131
Pogue (1915) also defined:
“Mottled matrix is a turquois matrix showing two shades of blue (or green), and may or may not contain foreign matter (see frontispiece, Fig. 2).”
— Pogue (1915), p. 131
From the Library: Branson, Turquoise: The Gem of the Centuries (1975)
1975 primary source. Anything described as current here describes 1975, not today.
Branson (1975) described what spider web actually is:
“Spider web is made up of small nuggets cemented together with natural rock or matrix.”
— Branson (1975), p. 6
And why it looks the way it does, in Branson's (1975) words:
“When cut through, the aggregate mass of nuggets resembles spider web.”
— Branson (1975), p. 6
According to Branson (1975, p. 6), most mines produced some spider web, while a few produced almost all spider web of varying quality; he pictured examples from Carico Lake, Red Mountain, No. 8, Timberline, Lone Mountain, Pilot Mountain, Godber and Kingman.
From the Library: How Matrix Became a Selling Point (Chambless & Ryan, 2021)
2021 primary source. Anything described as current here describes 2021, not today.
Chambless & Ryan (2021) weigh the part matrix played in the Great American Turquoise Rush:
“The presence of matrix was certainly a major factor in limiting production because buyers favored only the clear blue stone.”
— Chambless & Ryan (2021), p. 139 [3]
According to Chambless & Ryan (2021, p. 139), matrix was not the main cause of the price collapse at the end of the decade. The main causes were the financial crisis of 1907, the recession of 1908 that followed it, and a change in jewelry fashion. [3]
According to Chambless & Ryan (2021, p. 140), Mineral Park was where matrix turquoise was first marketed as special in its own right, even superior to clear blue. Clear blue was hard to find in large pieces, so it was cut small and set with other small stones. Matrix allowed larger stones and new designs, which suited the developing Indian jewelry trade. [3]
Chambless & Ryan (2021) reproduce the Southwest Turquoise Company's 1908 catalog:
“The matrix turquoise is the most popular on account of the beautiful marking.”
— Chambless & Ryan (2021), p. 140 [3]
According to Chambless & Ryan (2021, p. 142), the Arizona Turquoise Company's 1908 catalog explained that instead of grinding away the matrix, it cut and polished matrix and turquoise together. The same rough then produced one large matrix stone that cost no more than a much smaller pure one. [3]
From the Library: Lowry, Turquoise: The World Story of a Fascinating Gemstone (2010)
2010 primary source. Anything described as current here describes 2010, not today.
Lowry (2010) cautions that a famous pattern is not a mine signature:
“There are certain mines that have become famous for a matrix pattern. This does not necessarily mean that every turquoise with that matrix pattern only came from one mine.”
— Lowry (2010), p. 118 [4]
According to Lowry (2010, p. 118), many beginning buyers assume a stone with matrix must be natural, but when low- and medium-grade chalk turquoise is processed, its matrix is already part of the stone, so treated turquoise can show real matrix too. [4]
Lowry (2010) adds a warning about imitations:
“Pure plastics can have pyrites and other rocks or colored dyes added that imitate a natural matrix. There are also many cabochons that have a "filled" matrix.”
— Lowry (2010), p. 118 [4]
According to Lowry (2010, p. 188), matrix is graded by how symmetrical and well placed it is: low-grade matrix is when host rock dominates the stone; spiderweb or eggshell, an evenly placed pattern, is the rarest; waterweb is a lightly defined web from pale host rock or, more often, darker turquoise spheres around lighter ones; and picture rock forms a shape like a country or a tree. [4]
From the Library: Indian Arts and Crafts Board, Indian Arts and Crafts Act: Turquoise consumer brochure (2010)
2010 primary source. Anything described as current here describes 2010, not today.
The Indian Arts and Crafts Board (2010) described matrix for buyers:
“If a matrix is present, it will appear as tiny veins or dots of other rock within the turquoise, which can be golden, brown, black, white, or sienna in color.”
— Indian Arts and Crafts Board (2010), p. 2 [5]
On the most prized pattern, the Indian Arts and Crafts Board (2010) wrote:
“The rarest matrix, “spider web” turquoise, has a natural and uniform matrix that is evenly laced throughout the gemstone.”
— Indian Arts and Crafts Board (2010), p. 2 [5]
From the Library: Ryan & Chambless, Turquoise in America Part Two: 1910–1990 (2020)
2020 primary source. Anything described as current here describes 2020, not today.
Ryan & Chambless (2020) explain why most turquoise carries matrix:
“It occurs as both veins and pockets, but almost always within an underlying matrix.”
— Ryan & Chambless (2020), p. 27 [6]
According to Ryan & Chambless (2020, p. 27), miners of the 1890-1910 turquoise rush found far more turquoise in matrix, ranging from deep blue to green, than clear sky-blue stone; toward the end of the rush companies set out to build a market for matrix, which sold for a fraction of the price of clear blue. [6]
A 1901 advertisement by the Denver lapidary George Bell, quoted by Ryan & Chambless (2020), pitched matrix as the same stone:
“Matrix turquoise is cut from the same beautiful blue stone as the clear turquoise that has for countless ages been one of the most highly treasured gems.”
— Ryan & Chambless (2020), p. 27 [6]
According to Ryan & Chambless (2020, p. 28), the Southwest Turquoise Company's 1908 catalog, which praised its Mineral Park "cobweb turquoise" above all others, is perhaps the first reference to what, as of 2020, was considered the most desirable and expensive turquoise, the dark web deep blue. [6]
From the Library: Lowry, Turquoise Unearthed: An Illustrated Guide (2002)
2002 primary source. Anything described as current here describes 2002, not today.
Lowry (2002) on gold-coloured matrix:
“What may appear to be gold in the matrix is usually iron or copper pyrites (fool's gold).”
— Lowry (2002), p. 35 [7]
According to Lowry (2002, p. 35), in grading, a stone whose matrix pattern is evenly distributed is worth more than one with an uneven, "blotchy" matrix. [7]
Lowry (2002) named the spiderweb mines:
“Mines that are particularly noted for producing fine spider web turquoise are Number 8, Lone Mountain, and Lander Blue.”
— Lowry (2002), p. 35 [7]
Lowry (2002), describing dendrite turquoise as exceedingly rare:
“The fern-like pattern in the matrix is produced by the crystallization of a foreign mineral, usually an oxide of manganese, at the time the turquoise itself is being formed.”
— Lowry (2002), p. 42 [7]
From the Library: Jacka, Navajo Jewelry: A Legacy of Silver and Stone (1995)
1995 primary source. Anything described as current here describes 1995, not today.
Lois Essary Jacka, writing in 1995:
“In this country, turquoise with matrix is very desirable, especially the delicate "spiderweb" designs. Although it varies in color, texture, and natural design, the matrix adds contrast and enhances the beauty of the turquoise stone.”
— Jacka (1995), p. 78 [8]
From the Library: Welch, Indian Jewelry (1973)
1973 primary source. Anything described as current here describes 1973, not today.
As of 1973, Welch described a split over matrix:
“Many collectors and curators feel that turquoise with matrix (brownish lines and patterns) are more desirable. However, I agree with the Indians.”
— Welch (1973), p. 53 [9]
Welch (1973, p. 53) said that she, like the Navajo and Zuni buyers she had just described, liked her stones free of matrix and pure in colour. [9]
Field Notes by Mateo James
Our page calls spiderweb the most valuable pattern, but in 1915 Pogue wrote that matrix, however attractive, never commands the price of pure turquoise. Chambless & Ryan describe the same older market, in which the Persian non-matrix sky-blue stone was considered the only turquoise of value, and I tend to side with Chambless & Ryan on that history. The American grading the Lowrys describe today prizes a fine spiderweb instead, so the two views come from different eras of the market.
Sources
- Branson, Oscar T. Turquoise: The Gem of the Centuries. Santa Fe: Treasure Chest Publications, 1975. Cited by printed page. Statements describe conditions as of 1975.
- Pogue, Joseph E. The Turquois: A Study of Its History, Mineralogy, Geology, Ethnology, Archaeology, Mythology, Folklore, and Technology. Memoirs of the National Academy of Sciences, Vol. XII, Part II, Third Memoir. Washington, 1915. Public domain. Cited by printed page. Statements describe conditions as of 1915.
- Chambless, Philip, and Mike Ryan II. Turquoise in America, Part One: The Great American Turquoise Rush, 1890–1910. Revised first edition. Callais Press, 2021. Cited by printed page. Statements describe conditions as of 2021.
- Lowry, Joe Dan, and Joe P. Lowry. Turquoise: The World Story of a Fascinating Gemstone. Layton, UT: Gibbs Smith, 2010. Cited by printed page. Statements describe conditions as of 2010.
- U.S. Department of the Interior, Indian Arts and Crafts Board, with Joe Dan Lowry, Turquoise Museum, Albuquerque. Indian Arts and Crafts Act [turquoise consumer brochure]. Washington, DC: Indian Arts and Crafts Board, [2010]. GPO catalog gpo58769. Independence note: the Board states it "collaborated with Mr. Joe Dan Lowry, of the Turquoise Museum" on the turquoise information, so on turquoise it is not independent of Lowry (2010). Cited by printed page. Statements describe conditions as of 2010.
- Ryan, Mike, II, and Philip Chambless. Turquoise in America, Part Two: 1910–1990. Callais Press, 2020. Cited by printed page. Statements describe conditions as of 2020.
- Lowry, Joe Dan, and Joe P. Lowry. Turquoise Unearthed: An Illustrated Guide. Photography by Mark Nohl. Tucson, AZ: Rio Nuevo Publishers, 2002. Cited by printed page. Statements describe conditions as of 2002.
- Jacka, Lois Essary. Navajo Jewelry: A Legacy of Silver and Stone. Photographs by Jerry Jacka. Flagstaff: Northland Publishing, 1995. Cited by printed page. Statements describe conditions as of 1995.
- Welch, Frankie. Indian Jewelry: How To Wear, Buy and Treasure America's First Fashion Pieces. McLean, VA: EPM Publications, Inc., 1973. Cited by printed page. Statements describe conditions as of 1973.
