Uncovering the Mysteries of Green Chinese Turquoise.
- Jul 14
- 11 min read
Radioactive Turquoise, Uncovering the Mysteries of Green Chinese Turquoise
Neil Ray, West Texas Analytical Laboratory, Geochemist & Mineralogist
China has a rich heritage and culture of turquoise and it was likely a commodity that was routinely traded on the Silk Road and was considered a stone of spiritual significance in the ancient world. During the Cold War China was considered a closed society and contact with foreigners was discouraged. The story of the introduction of Chinese turquoise to the US market during the late 1980’s is found in Chapter Five, “First Contact’ in Turquoise in America Part Two, 1910-1990 by Mike Ryan II and Philip Chambless. The Yungai Temple Mine, aka Cloud Mountain, was an historical center of turquoise mining. Production has ceased at that location with the formation of a Turquoise National Park and museum. Today there are many additional turquoise mines in China with marketing names applied for various new material surfacing to the market. Unfortunately, mining provenance is not as organized as it is with American turquoise and names given to a specific turquoise may be material from the same or different mine within the region sold under a new marketable name. Recently, a small amount of green stabilized turquoise, confirmed as Chinese, was discovered that has a surprising property in that it is mildly radioactive. To ascertain the origin of this unusual turquoise it was compared to green turquoise from Bamboo Mountain and from Treasure Mountain. Bamboo Mountain is sourced close to the famous deposits of Yungai and Treasure Mountain is sourced near Qingu. To compare the differences between the turquoise of known provenance and the unknown radioactive Chinese turquoise, chemical analyses, mineralogy, as well as a gamma energy spectrum for the types of radionuclides emitted are determined.
Chemical analysis of turquoise is performed using a Thermo Niton XRF analyzer. X-ray fluorescence is advantageous in that it is not destructive and provides an analysis of every element from magnesium to uranium on the periodic table. Unfortunately, XRF doesn’t measure light elements such as sodium and lithium, or differentiate between iron 2+ or iron 3+. To overcome the issue of missing light elements, a complex mathematical algorithm known as P3M was developed to calculate sodium, lithium, and differentiate iron. P3M also determines mineralogy using elemental allocation and pressure/temperature constraints using geothermometer/geobarometer calculations. An extensive database of turquoise has been compiled with numerous samples from over 150+ mines, within the U.S. and international localities. Ternary plots and trace element variations are used as indicators to compare unknown turquoise against samples of verifiable provenance to determine the origin. The use of ternary plots and trace element ratios allow for the delineation of origin even if a variation in chemistry exists within the same stone. The pilot study for the approach and methodology of the initial development of the algorithm, Determining the Identification and Grade of Turquoise using Trace Element Chemistry by Neil Ray and Mike Ryan II, can be downloaded from turquoiseinamerica.com. Gamma and beta emission is determined using a Radiacode 103 handheld scintillometer to determine the spectrum of radionuclide isotopes, particularly with comparisons in uranium concentrations obtained from XRF analysis.
Uranium is uncommon in turquoise, with concentrations typically less than 20 ppm, which is 0.002%. Some exceptions exist, in fact uranium is a useful indicator element to identify Lander Blue, which typically contains greater than 30 ppm uranium. All Chinese turquoise has even higher concentrations of uranium, often exceeding 100 ppm. It is important to note that even at 100 ppm (0.01%), it is still a very low amount of uranium and not considered radioactive by any means and below measurement on a conventional Geiger counter or scintillometer, unless long term measurements were made for several days using adequate shielding to block background radiation interference. However, the unknown Chinese turquoise in question has concentrations of uranium exceeding 1000 ppm (0.1%). At this concentration radiation can be determined by a scintillometer, but the amount is still low and the material is considered safe to handle. In fact, the concentration of uranium is comparable with that of vintage translucent uranium glass, which gives off nearly the same amount of radiation. Chemical analyses of the three unknown specimens are detailed in the table below. Uranium concentrations are more prominent in the matrix, thus specimens #1 and #3 were analyzed on two different spots; analysis “b” represents the darker matrix. It can be seen from the data table that the matrix contains significantly more uranium, coupled with higher amounts of calcium and less amounts of copper/phosphorus. Despite the green coloration, the specimens contain a considerably low amount of iron and the green coloration is most certainly due to elevated chromium, vanadium, and zinc.
Major and Trace Element Chemistry of Radioactive Chinese Turquoise of Unknown Provenance, Specimens #1, #2, #3.
The matrix of the unknown specimens consists of illite type clays and pyrite, which likely necessitated the need for stabilization of these specimens. Specimen #3 contains planerite within the matrix, which is a turquoise group mineral containing less copper than turquoise. The matrix of this specimen also contains significant uraninite. The matrix of specimen #1 also contains significant uranium, however unlike specimen #3 the uranium is within an exotic phase not noted in the list of quantifiable minerals. This mineral species is likely an alteration product of uraninite and could consist of uranocircite, which is a uranium phosphate derived from interactions of weathered uraninite with copper phosphorus rich fluids or a variety of uranium sulfates such as zippeite from the available sulfur formed at the expense of the degradation of pyrite. Specimen #3 is particularly interesting in that it also contains perovskite, which is a rare mineral common to the earth’s mantle or a product of contact metamorphism of carbonate skarns and an accessory mineral in silica deficient rocks. Additionally, specimen #3 is absent of quartz, where the primary silica minerals are confined to feldspar and clays.
Comparisons of the unknown specimen set made to turquoise from Bamboo Mountain and Treasure Mountain show geochemical similarities indicating that the material is from the same region but significant differences exist to indicate that neither locality is the source of the unknown material. Four cabochons of Bamboo Mountain and three cabochons of Treasure Mountain were compared for differences in geochemistry and mineralogy.
Treasure Mountain, From Left to Right, Specimens TM#1, TM#2, TM#3.
Bamboo Mountain, From Left to Right, Specimens BM#1, BM#2, BM#3, BM#4.
Both Bamboo Mountain and Treasure Mountain contain concentrations of uranium that are typical for Chinese turquoise, with values less than or approaching 100 ppm. Both turquoise sets contain elevated amounts of selenium, characteristic of copper hosted mineralization and both specimen sets also contain considerably more sulfur and iron than the unknown specimens, with total iron concentrations exceeding 20%. Moreover, Treasure Mountain is notably higher in iron, with most of the iron existing as iron 2+. The elevated amounts of barium and vanadium are comparable to concentrations observed in turquoise from other Chinese localities, but both specimen sets show more arsenic, lead, and molybdenum. Treasure Mountain is also enriched in niobium and rubidium in comparison to Bamboo Mountain, whereas Bamboo Mountain contains more antimony and zinc. Such variances are effectively used to differentiate the two sources of turquoise. The unknown specimens share similar aspects of both Bamboo Mountain and Treasure Mountain, indicating a nearby origin, but distinctively different to qualify as originating from either locality.
Major and Trace Element Chemistry of Treasure Mountain and Bamboo Mountain, Treasure Mountain Specimens #TM1, #TM2, #TM3 and Bamboo Mountain BM#1, BM#2, BM#3, BM#4.
The chemical composition of Treasure Mountain also attests to its unusual mineralogy, with TM#1 consisting of turquoise in a clay matrix, but TM#2 and TM#3 are composed largely of chalcosiderite. TM#3 consists of additional feldspar, reflective of the host rock matrix. Treasure Mountain also contains considerably more pyrite that has likely degraded and is altered to jarosite. Conversely, Bamboo Mountain consists of greater than 70% turquoise, quartz, and minor feldspar. As it can be observed both specimen sets vary considerably from the unknown specimen set, which contains more quartz and turquoise gradation to planerite. Additionally, low uranium concentrations show insignificant amounts of uraninite or uranium bearing minerals, when compared to the unknown specimen set.
Mineralogy of Treasure Mountain and Bamboo Mountain, Treasure Mountain Specimens #TM1, #TM2, #TM3 and Bamboo Mountain BM#1, BM#2, BM#3, BM#4.
The high concentrations of uranium in the unknown specimen set attain to measurable amounts of gamma and beta emission, which can be quantified using an isotope scintillometer. Spectra of the unknown specimens were measured using a Radiacode 103 with 1-hour acquisitions per sample and compared against background radiation. To signify the difference between the unknowns and non-radioactive turquoise, one specimen of Bamboo Mountain #1 was added for comparison. Additionally, to quantify the amount of radiation against something more well known, a vintage uranium glass candle holder was added as a control sample. The prominent peaks are lead-214 and bismuth-214, which are part of the natural decay chain of uranium-238. Lead-214 undergoes beta decay into bismuth-214 and bismuth-214 also undergoes beta decay to polonium-214, which isn’t detected by the scintillometer as it is strictly an alpha emitter, which can’t be quantified by the Radiacode 103. It can be observed that uranium glass is comparable to the radiation emission from the unknown turquoise specimen set. Although, uranium glass has a slightly higher number of counts per second than the specimens, the specimens have a higher dose rate in μR/h. Though both the uranium glass and specimens have a similar concentration of uranium, the difference in dose rate is due to the type of uranium. The uranium glass is likely made from depleted uranium, whereas the specimens contain unrefined uranium. Such differences can be seen in the specimens which contain higher peaks of uranium-235 and radium-226 than the glass. It can also be seen that the Bamboo Mountain specimen is barely above background. Again, the amounts of uranium and radionuclides in the unknown specimen set are considered very low and the turquoise is no different in radioactivity to that of uranium glass. It could be safely worn as jewelry, provided that the jewelry piece is not worn continuously every day and like uranium glass care should be taken when performing lapidary work on materials that can generate radioactive dust, which can cause serious complications if breathed in. It’s always advisable to wear a mask when performing lapidary work, particularly on materials that can create toxic dust.
Radiacode 103 spectra of unknown specimen set (#1, #2, #3) versus Bamboo Mountain (#1), uranium glass candle holder (U-glass), and background.
West Texas Analytical Laboratory is not affiliated with Turquoise in America and does not receive economic compensation for any promotion nor pay for any promotion. I am a geochemist with over 15 years laboratory experience and graduate level research on metasomatic and hydrothermal emplacement. If you are interested in submitting samples for analysis, you may contact West Texas Laboratory at 580-977-6951. The cost is $65 for a comprehensive analysis that includes mineralogy, origin, grade, and more or $35 for a simple chemical analysis to identify if it is turquoise and natural or treated.
Comments