Turquoise Doppelgängers: Why Do Some Mines Look Alike?
As you may know turquoise stones are like snowflakes, no two are the same. When turquoise is pulled from the earth it has a unique fingerprint. This is caused by unique elements that affect the stone during formation, such as host rock composition, elevation, pressure and temperature. This causes the stones to display variations of color and matrix patterns. Stones that are formed in the same mine are usually the product of similar host rock material and are exposed to similar environmental conditions. Common color and pattern variations can be observed being produced from specific mines. These stereotypical appearances are usually then associated with that mine. This is a very useful tool for identifying the origin of a turquoise stone. Experienced collectors and dealers in the industry can often see a turquoise stone and give you good idea what mine it came from, sometimes even the year it was mined.
Even though experts can get really good at identifying turquoise stones this way, it is almost impossible to be 100% accurate. Turquoise doppelgangers exist out there to fool us all. As turquoise veins run through the earth they hit inconsistent patches of rocks and other elements. These not only change the host stone composition, but also can affect the pressure or temperature. This causes variations or the stone appearance that can mimic other mines.
Here are some examples of some stones that look very much alike. Can you tell the difference?
In this first image some of the sets of stones are from the Royston Turquoise Mine and the other is from the Ajax mine. The greenish coloration is from the concentration of iron in the host material during formation.
This second image is a set of stones from the Candaleria mine and the other is from Lone mountain turquoise mine. The blue color is usually an indication for higher concentrations for aluminum during formation.
The final picture is an image of stones from the Royston mine and the Easter Blue turquoise mine. These mines are in very near in proximity to each other, both in the Royston district in Nevada. I wanted to note that the Royston mine was also used in the first picture and even though some of these stones came from the same mine they look very different.
To learn more about turquoise mines color and pattern variations please check out these links.
From the Library: Pogue, The Turquois (1915)
1915 primary source. Anything described as current here describes 1915, not today.
Pogue (1915) described deposits where turquoise straddles two kinds of rock:
“In the Mohave Desert and at several other localities in Nevada the turquois lies along the contact between igneous and sedimentary (or metamorphic) rocks, occurring in each. The portion in the igneous rock is identical in all its associates and relations with turquois of type 1.”
— Pogue (1915), p. 66
Writing in 1915, Pogue quoted the geologist Lindgren, who, after studying the Cerrillos deposits,
“believes it safe to assert that turquois is not a primary vein mineral, but is formed by surface waters of ordinary temperature descending through altered and mineralized rocks.”
— Pogue (1915), p. 62
Pogue's own 1915 verdict, with its caveat:
“The weight of evidence therefore favors a superficial origin for turquois of type 1, although some occurrences present features, notably a close association with abundant sericite, not readily compatible with a formation from descending meteoric waters.”
— Pogue (1915), p. 64
Identifying a mine by eye is an old claim. Pogue (1915) translated Muhammed Ibn Mansur, writing about 1300:
“The turquois is divided according to its different sources into different qualities, and experts, as soon as they see a turquois, can tell from what mine it came.”
— Pogue (1915), p. 71
Ibn Mansur tied each grade to a mine, in Pogue's 1915 translation:
“The best mines are at Nishapur; there are seven mines, from which come the seven grades of turquois mentioned.”
— Pogue (1915), p. 72
From the Library: Branson, Turquoise: The Gem of the Centuries (1975)
1975 primary source. Anything described as current here describes 1975, not today.
The problem is not new. Writing in 1975 about Blue Gem's blue-to-green stones, Branson noted:
“This has become such a distinguishing feature of Blue Gem turquoise, that similar stones from other mines are often sold as "Blue Gem" turquoise.”
— Branson (1975), p. 16
According to Branson (1975, p. 2), stones from one mine often resemble those from another very closely, and in some cases even an expert or a lapidary could not tell them apart.
Captioning a row of Persian stones from the mines near Mashad, Branson (1975) warned against the opposite shortcut:
“Most all mines show a great diversity of colors, so one should not say that stones from a certain mine are all one color.”
— Branson (1975), p. 3
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.
Ron Alexander, who imported several tons of turquoise from an iron mine at Ma'anshan in Anhui Province, told Ryan & Chambless (2020):
“There's some Ma'anshan you would swear is high-grade Bisbee turquoise.”
— Ryan & Chambless (2020), p. 263 [3]
Ron Alexander recalled, in an interview published by Ryan & Chambless (2020, p. 261), that when he first brought large lots of glassy, hard Chinese spiderweb to the US in the late 1980s, many buyers did not take it for fake but for some other stone that merely looked like turquoise. [3]
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:
“To further confuse identification, more than one mine may produce turquoise with similar colors and matrix characteristics.”
— Jacka (1995), p. 78 [4]
Field Notes by Mateo James
I notice our article lists pressure and temperature among the things that shape a stone during formation. Pogue, writing in 1915, weighed the evidence toward cool surface water seeping down through rock near the surface, and he quoted Lindgren that turquoise forms from surface waters “of ordinary temperature.” Pogue did allow that some deposits don’t fit that picture neatly, so the question isn’t fully closed, but his account doesn’t point to heat and pressure.
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.
- 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.
- 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.
