Turquoise from the Orogrande Mining District, NM – Long Forgotten Treasure from the DeMeules and Iron Mask Mine

Neil Ray, West Texas Analytical Laboratory, Geochemist & Mineralogist

(Neil Ray has been a guest contributor at Turquoise in America. This article continues his scientific research with XRF, X-Ray Florescence for the purpose of turquoise identification, treatment and grade. Neither Philip, myself or TIA have any affiliation with Neil or West Texas Analytical. This article is for information only.)

New Mexico has a wealth of turquoise deposits, however when someone thinks turquoise the most prevalent New Mexico mines that come to attention is Cerrillos, Tyrone, or Hachita.  Few people have heard of turquoise from the Orogrande Mining District, which is located directly south of Alamogordo, near the White Sands National Park.  The Orogrande Mining district has a rich history that can be found in Turquoise in America Part 1, The Great American Turquoise Rush, 1890-1910 by Philip Chambless and Mike Ryan II.    Archaeological evidence was found of pre Colonial mining for turquoise in the region by Native Americans long before commercial mining exploration began in the Jarilla Mountains.  In 1892 William Hidden (miner in which the gem variety of spodumene Hiddenite is named after) was prospecting for turquoise in the Hachita region but gave up his efforts when little high-grade material was found.  He refocused his attention on the Jarilla Mountains, uncovering around fifty kilograms of high-quality turquoise that found a market demand in New York and London.  Mining ceased for several years until Amos J. DeMeules, a gold miner who already had several claims in the Jarilla Mountains, found an abandoned turquoise mine and once again began to produce a wealth of high-quality turquoise that the market had not yet seen before at that time.  Certainly a few years later, the Orogrande Mining District got its rise to fame in 1905 when a large gold nugget was uncovered in the nearby Jarilla Mountains, which spawned the name Orogrande meaning “big gold”.  In addition to turquoise the Orogrande Mining District produces a wealth of mineralization including fine crystallized garnets, smithsonite, and malachite to name a few species.  During the midcentury turquoise mining was proceeded by commercial mining for iron and copper and most claims today are consequently closed with no future operational plans. 

As with many commercial mining operations, repurposed mining operations considered secondary turquoise an unprofitable waste by-product, thus making sourcing Orogrande turquoise next to impossible as very little is available on the market.  An online search for Orogrande turquoise returned no available material for sale in rough or in jewelry pieces.  Certainly, small amounts of turquoise specimens and rough may likely be acquired from local dealers in the area, but it is simply not commercially available on the market.  There are two documented types of turquoise deposits in the northern Orogrande Mining District, which are considered the DeMeules and Iron Mask Mine.  If one was to find Orogrande turquoise for sale, the DeMeules Mine would certainly be the most available material, as the mine is now considered a gemstone site that has been prominently collected for turquoise by many rockhounding enthusiasts over the years.  Turquoise from the Iron Mask is considered rarer as its currently under private claim, having been sporadically commercially mined from 1915 up until 1980.  The Iron Mask Mine was also known as the Iron Duke and Lara Mine and is home to many adjacent mining claims that include the Tiffany Mine, Alabama Group, and various prospects within the Jarilla Mountains.  Though both types of Orogrande turquoise are well documented in publications by the New Mexico Geological Survey, a further need of research in the geochemical variances is needed to highlight the uniqueness of Orogrande turquoise.

Background on Testing Methods

Several specimens of Iron Mask rough, representing the diversity of the turquoise were selected for geochemical analysis and a comparison of the Iron Mask material was made to three select turquoise specimens from the DeMeules Mine for trace element similarities and variances.  Finally, a few select Iron Mask specimens were cut into cabochons and a follow-up chemical analysis was performed for comparison to the rough material.  Geochemical modelling is performed using P3M software, which was developed over the course of 10 years that uses major and minor trace element chemistry to calculate mineral percents in various rock types, compiling data on 100 different mineral species.  The software uses complex algorithms that assign elements to minerals based on lithology and associated calculated pressure/temperature conditions.  There are a lot of laboratory methods to acquire a chemical analysis on a whole rock, the standard method is to grind the sample and digest it in strong acids by weight and analyze it on an instrument known as an ICP-OES, which stands for inductively coupled plasma optical emission spectrometer.  Though ICP is certainly the most accurate method available with the possibility to analyze almost every element on the periodic table, destructive testing is not a desirable choice for rarer geological material.  The accepted method that is widely used is Xray fluorescence (XRF), which is non-destructive and reliable for elements from magnesium to uranium.  Since an XRF is used to determine elements, it is important to select the correct analyzer, that has a large detector capable of measuring the bare minimum of magnesium and light elements such as silicon and aluminum.  It is also equally important to select an analyzer with the proper modes, such as both mining and soil mode.  Soil mode alone will not be appropriate due to matrix differences, analyzing whole rock versus crushed rock or sediment.  Unfortunately, XRF does not detect lighter elements, such as sodium which is very important for mineralogical determinations.  To overcome sodium, an additional algorithm was developed to calculate sodium based on major element allocations.  Additionally, it is also important to distinguish between iron 2+ and iron 3+, which also an XRF analyzer cannot achieve, thus an additional algorithm was developed to differentiate between both forms of iron.  Finally, though lithium concentrations are very low in turquoise a final algorithm was developed to determine lithium concentrations for lithium exploration of pegmatites.  These algorithms have been tested on material analyzed by ICP as well as chemical titration and verified on over 40 published peer reviewed papers containing chemical analyses of various rock types, with over an 85% accuracy.  The major and minor elements are used to calculate the reported 100 mineral species, again verified by peer reviewed published data or additional laboratory analyses.   Most of the minerals that are reported are not found in turquoise, only becoming more important in the examination of other rock types such as igneous and metamorphic rocks.  Mineralogical determination is invaluable as to determine mineralogy in rocks, a separate instrument known as xray diffraction is required, which too is a destructive testing method. 

Geochemistry of the Iron Mask and DeMeules turquoise 

Eleven specimens of rough comprising a diversity in coloration and matrix patterns were selected for analysis.  Some of the rough appears stabilized with yellow globules of epoxy on the surface, however it is noted that sometimes turquoise that is initially collected is coated with epoxy on the exterior of the specimen to preserve the color for long term storage.  This process becomes especially important with turquoise that contains significant sulfur, which can react with moisture in the air over time creating sulfuric acid that may discolor and degrade the turquoise and turn it into powder.  It is important to note that this process is not considered stabilization, as only the exterior of the stone is coated, and it doesn’t penetrate the interior of the stone as the stabilization process would do.  To verify that the epoxy is only a surface coating, cabochons were made from a few select specimens and reanalyzed to show geochemical variances.  The Iron Mask specimens certainly display a diversity in coloration, which can be seen in specimen #1, which is bluish green and specimens #4,#5,& #9 that are entirely sky blue.  Specimen #2 has intricate webbing that is somewhat reminiscent of China Cloud Mountain turquoise and specimen #10 is truly the oddest in coloration, with an almost pistachio green color.  Such diversity makes this turquoise unique and certainly compelling.  The specimens of DeMeules turquoise show a degree of variation in appearance as well, but the variation is not as pronounced as the Iron Mask specimens.  The bulk and trace element analysis of each specimen is provided in the proceeding data tables.       

Figure 1a – Iron Mask turquoise rough, specimens #1 - #7, from left to right and top to bottom.

Figure 1b – Iron Mask turquoise rough, specimens #8 - #11, from left to right and top to bottom.

Figure 1c – DeMeules turquoise, specimens #1 - #3, from left to right and top to bottom.

Table 1a – Bulk and trace element chemistry of Iron Mask specimens #1-#11

Wt. %	IM #1	IM #2	IM #3	IM #4	IM #5	IM #6	IM #7	IM #8	IM #9	IM #10	IM #11
SiO2	10.5213	1.9018	9.9648	9.7716	15.9181	6.9114	31.7937	8.5813	4.5227	9.3337	7.2850
Al2O3	20.4966	34.3705	32.4592	18.0796	21.6707	32.9380	30.6579	20.3462	33.3488	8.6461	36.9168
MgO	1.4907	1.6946	1.1564	3.2292	1.6376	1.8291	0.9539	1.2828	1.5408	3.8321	1.6011
CaO	0.5265	0.2706	0.3182	14.9834	5.9253	0.3132	0.0848	0.0526	0.5999	10.2285	0.4566
K2O	0.0175	0.0773	0.1461	0.3708	0.1391	0.7263	0.0109	0.8035	0.0887	0.2963	0.4105
Na2O	1.2727	0.8430	0.1204	1.3172	0.1131	0.0276	4.0615	0.8303	0.1135	0.2134	0.5618
P2O5	17.7898	27.5686	16.7087	2.8297	6.0945	16.2472	4.5020	19.4968	25.9653	7.3432	20.5940
TiO2	0.0319	0.0089	0.1130	0.0171	0.2173	0.1252	0.0492	0.0909	0.0389	0.1998	0.0783
FeO	3.5543	0.3393	0.0491	1.8581	0.2700	1.2470	1.9868	3.7424	0.1703	2.3270	0.4847
Fe2O3	4.9730	3.4613	0.4092	0.7905	1.8072	10.6010	2.4913	0.0360	1.8358	18.8897	3.8767
S	0.9089	0.2841	0.9955	16.3918	7.2894	1.2548	0.1507	0.2962	0.5636	10.8375	1.0565
Cl	0.0265	0.1439	0.0033	0.2245	0.2375	0.2462	0.0069	0.0034	0.0652	0.0890	0.1229
Ppm Wt.
Sr	1066	203	722	20	102	181	10	11	1144	622	89
Ba	446	472	604	114	109	183	33	1307	359	165	514
Rb	2	5	2	5	13	10	2	37	3	2	3
Zr	8	4	6	19	116	72	2	36	8	7	3
Mo	3	4	3	3	3	8	2	161	10	4	3
V	171	27	128	49	48	94	60	51	119	197	31
Ni	43	28	26	20	18	44	16	27	28	52	29
Cu	39844	66800	54148	26366	16686	58542	10896	46427	65826	36516	67699
Zn	1225	406	2806	296	147	264	383	458	419	254	338
Cr	171	120	355	65	84	158	160	51	278	281	129
Pb	106	6	6	6	5	24	3	5	49	26	5
As	27	60	120	59	25	205	34	156	9	39	46
W	78	239	493	201	150	66	111	474	825	70	90
Sb	14	10	14	9	8	16	7	58	13	17	19
Sn	15	46	80	64	52	102	6	51	16	17	51
Ag	10	8	11	7	6	8	6	18	17	11	13
Bi	7	5	6	4	8	14	3	6	6	7	6
Nb	3	3	2	2	6	7	2	2	3	3	3
U	9	33	7	6	9	21	3	6	26	9	9
Th	5	2	4	2	4	10	2	2	3	3	3
Se	316	4	4	3	3	265	2	4	5	295	4
Li	0	0	0	0	13	0	0	0	0	0	0

Table 1b – Bulk and trace element chemistry of DeMeules specimens #1-#3

Wt. %	DM #1	DM #2	DM #3
SiO2	10.6514	73.1696	8.8019
Al2O3	45.5900	15.0680	41.4520
MgO	1.9345	3.2992	2.5674
CaO	0.5661	1.4458	1.0223
K2O	0.1023	0.1380	0.2159
Na2O	0.8261	0.9554	0.0138
P2O5	29.4505	7.7603	24.8957
TiO2	0.0400	0.0218	0.0197
FeO	0.5245	5.8633	1.9857
Fe2O3	3.7294	9.7184	17.4921
S	0.1676	0.4638	0.9613
Cl	0.0033	0.0421	0.0038
Ppm Wt.
Sr	290	291	315
Ba	1590	133	191
Rb	3	2	2
Zr	4	27	8
Mo	3	391	176
V	38	92	192
Ni	28	45	55
Cu	54094	15496	55724
Zn	1225	131	142
Cr	96	358	532
Pb	96	73	28
As	30	42	70
W	322	71	78
Sb	12	24	19
Sn	13	24	18
Ag	11	12	9
Bi	6	6	6
Nb	2	3	3
U	6	15	53
Th	3	5	0
Se	4	261	297
Li	0	0	0

Just as the appearance of the Iron Mask specimens show diversity, there is also a considerable amount of variation in the geochemistry of the specimens as well.  The Iron Mask specimens show notably higher calcium and sulfur concentrations than that of the DeMeules specimens.  The presence of calcium and sulfur contributes to the unique mineralogy of the Iron Mask turquoise, which is attributed to both gypsum and jarosite.  Gypsum is associated with evaporite mineralization as well, which can also be observed in the elevated amounts of chlorine as halite in the Iron Mask specimens vs. the chlorine depletion in the DeMeules specimens.  Calcium, sulfur, and chlorine are geochemical fingerprints that can be used to distinguish between turquoise from both mine sets.   Another major difference between the two is although both sets contain significantly high concentrations of silicon, the DeMeules is slightly more elevated in silicon and is considered quartz rich.  DeMeules specimen #2 is over 70% SiO2 and is essentially composed entirely of quartz.  Interestingly enough iron exists predominantly as iron 3+ in both turquoise sets, with upwards of ten times more iron 3+ than that of iron 2+.  The differences in the Iron Mask and DeMeules turquoise is well documented by Virgil Lueth, Ph.D, mineralogist for the State of New Mexico.  Turquoise from the DeMeules occurs as veins in altered granite, which formed as low pH fluids converted feldspar into kaolinite and limonite.  Alternatively Iron Mask turquoise occurs mainly as nuggets that are said to have formed from hydrothermal alteration of a host phosphorus rich shale, which proceeded gypsum and halite precipitation.  Pyrite oxidation created low pH sulfate rich fluids, which percolated along fractures.  Analysis of the Iron Mask specimens show an aluminum/phosphorus ratio indicative of potential stabilization, however follow-up analysis of cut cabochons indicates that the epoxy is only a surface coating used to preserve the turquoise from long term storage and did not penetrate the interior of the specimens analyzed. 

Mineralogy of the Iron Mask and DeMeules turquoise 

     Table 2a – Mineralogy of Iron Mask specimens #1-#11

	IM #1	IM #2	IM #3	IM #4	IM #5	IM #6	IM #7	IM #8	IM #9	IM #10	IM #11
Quartz	10.95	0.00	8.87	20.57	24.28	5.94	54.43	3.48	2.89	10.24	4.23
Albite	3.27	0.00	1.17	0.00	0.00	0.00	6.21	2.38	0.00	0.02	1.52
Orthoclase	0.14	0.00	1.06	0.00	1.35	4.73	0.12	6.12	0.59	2.07	2.46
Perovskite	0.00	0.00	0.00	0.03	0.00	0.00	0.00	0.00	0.00	0.00	0.00
Magnesiochromite	0.00	0.00	0.06	0.01	0.02	0.02	0.00	0.00	0.04	0.04	0.02
Magnetite	0.00	0.04	0.00	0.00	0.00	0.00	0.00	0.02	0.00	0.00	0.00
Hematite	0.00	1.16	0.15	0.21	0.89	3.50	0.00	0.00	0.61	6.69	1.18
Rutile	0.00	0.00	0.14	0.00	0.36	0.14	0.00	0.00	0.04	0.24	0.08
Zircon	0.00	0.00	0.00	0.00	0.03	0.01	0.00	0.01	0.00	0.00	0.00
Turquoise	69.36	97.08	85.43	19.67	34.97	82.51	26.27	76.58	94.03	55.18	87.77
Calcite	0.00	0.00	0.00	1.55	0.00	0.00	0.00	0.00	0.00	0.25	0.00
Ankerite	0.00	0.00	0.00	0.00	5.59	0.00	0.00	0.00	0.00	0.00	0.00
Dolomite	0.00	0.00	0.00	0.67	0.00	0.00	0.00	0.00	0.00	0.27	0.00
Rhodochrosite	0.08	0.02	0.03	0.01	0.02	0.00	0.02	0.00	0.02	0.00	0.01
Azurite/Malachite	0.08	0.13	0.62	0.35	0.40	0.00	0.37	1.08	0.27	0.00	0.09
Halite	0.07	0.31	0.01	0.37	0.73	0.51	0.02	0.01	0.14	0.20	0.23
Fluorite	0.02	0.02	0.01	0.00	0.01	0.00	0.01	0.02	0.02	0.00	0.01
Anhydrite	0.00	0.00	0.00	44.95	8.95	0.00	0.00	0.00	0.00	2.41	0.00
Pyrite	2.27	0.56	2.25	3.69	6.40	2.57	0.53	0.64	1.14	7.69	1.96
Chlorite/Serpentine	0.00	0.56	0.00	1.21	0.00	0.00	0.00	0.47	0.00	0.00	0.00
Illite/Clays	6.15	0.00	0.00	0.00	5.26	0.00	6.77	8.90	0.00	0.00	0.35
Zoisite/Clinozoisite	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	1.84	0.00
Exotic Phases	0.00	0.00	0.00	6.16	10.69	0.00	0.00	0.00	0.00	12.84	0.00
Chalcopyrite	0.01	0.01	0.03	0.01	0.01	0.00	0.00	0.00	0.02	0.00	0.01
Bornite	0.07	0.07	0.04	0.02	0.03	0.00	0.00	0.00	0.06	0.00	0.08
Cuprite	0.00	0.00	0.00	0.51	0.00	0.00	0.00	0.00	0.00	0.00	0.00
Proustite	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.13	0.00	0.00	0.00
Arsenopyrite	0.00	0.00	0.03	0.00	0.00	0.05	0.00	0.00	0.00	0.00	0.00
Galena	0.02	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00
Molybdenite	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.03	0.00	0.00	0.00
Cassiterite	0.00	0.00	0.00	0.00	0.00	0.01	0.00	0.00	0.00	0.00	0.00
Scheelite	0.00	0.04	0.10	0.03	0.04	0.00	0.03	0.10	0.14	0.00	0.00
Limonite/Goethite	7.52	0.01	0.00	0.00	0.00	0.00	5.22	0.02	0.00	0.00	0.00
Pyrolusite	0.00	0.00	0.00	0.00	0.00	0.01	0.00	0.01	0.00	0.02	0.00

Table 2b – Mineralogy of DeMeules specimens #1-#3

	DM #1	DM #2	DM #3
Quartz	4.78	60.85	10.90
Albite	6.83	0.73	0.07
Orthoclase	0.60	0.66	1.40
Chromite	0.00	0.00	0.02
Ilmenite	0.08	0.04	0.00
Magnetite	0.44	0.00	0.00
Hematite	0.91	0.00	5.10
Turquoise	84.06	19.52	78.13
Crandallite	0.00	3.15	0.00
Rhodochrosite	0.01	0.00	0.00
Azurite/Malachite	0.10	0.00	0.00
Halite	0.01	0.08	0.01
Fluorite	0.01	0.00	0.00
Anhydrite	0.00	0.01	0.00
Barite	0.00	0.08	0.00
Pyrite	0.29	0.77	1.97
Chlorite/Serpentine	0.00	3.45	0.00
Illite/Clays	1.51	0.00	0.00
Chalcopyrite	0.01	0.00	0.00
Bornite	0.05	0.00	0.00
Scheelite	0.05	0.00	0.00
Limonite/Goethite	0.28	10.64	2.39
Pyrolusite	0.00	0.01	0.01

Some of the Iron Mask specimens contain considerably higher concentrations of gypsum and halite, particularly specimen #4, which is composed of almost 50% gypsum.  Halite concentrations approach 1% in the Iron Mask specimens that were analyzed, which certainly correlate as expected given the presence of gypsum and the likelihood of evaporite precipitation.  It should be noted that the P3M algorithm doesn’t quantify jarosite or alunite, which is displayed in the data table as exotic phases.  Although the iron concentrations are similar between both mine sets, it is interesting to note that the variation of iron mineralization is considerably different.  The Iron Mask contains pyrite and jarosite, with no limonite or only minor limonite (noted in specimens #1 & #7) whereas the DeMeules specimens show significantly higher concentrations of hematite and limonite, coupled with lower pyrite than the comparable Iron Mask specimens.  Iron Mask specimen #10 is the oddest sample that was analyzed, containing the highest amount of iron and sulfur, yielding the highest concentration of jarosite and pyrite, with additional secondary epidote.  Accessory sulfide mineralization and oxides are more prevalent in the Iron Mask specimens as well than that of the DeMeules specimens; the Iron Mask specimens contain more carbonates as secondary azurite.  The quartz concentration is extremely variable between both mine sets, with the DeMeules specimens having a slightly overall higher concentration of quartz.  It is interesting to note that a direct comparison between both mine sets of quartz rich or quartz deficient specimens indicate that the quartz deficient specimens such as Iron Mask #11 versus DeMeules #1 show that the quartz deficient DeMeules specimens contain more plagioclase and are lower in orthoclase than the comparable quartz deficient Iron Mask specimens.   The opposite is noted in quartz rich specimens such as Iron Mask #7 and DeMeules #2, where plagioclase in the Iron Mask specimen is higher than orthoclase.  It is interesting to note that the quartz rich DeMeules specimen #2 also contains crandallite, which was absent from all the Iron Mask specimens that were analyzed.  The variation in quartz and the presence of gypsum account for a slight variation in hardness between turquoise from both mines.  The DeMeules turquoise is slightly harder than that of the Iron Mask, attaining to the higher overall quartz content and the absence of soft minerals such as gypsum.  These mineralogical variations coincide with the New Mexico Geological surveys assessment of turquoise mineralization between both mines.  Lower quantities of orthoclase feldspar, coupled with higher limonite concentrations coincide with the proposed alteration of granite host rock by low pH fluids for the turquoise mineralization at the DeMeules Mine.  Conversely, the higher concentrations of pyrite and the presence of gypsum and halite support the assessment of hydrothermal alteration of phosphorus rich shale at the Iron Mask Mine, following post deposition of sulfates and evaporites.

The DeMeules specimens formed at a higher temperature than the Iron Mask specimens, with DeMeules temperatures of formation greater than 300C, whereas most of the Iron Mask specimens formed at temperatures considerably lower, below 300C.  Apart from the higher formation temperatures of Iron Mask specimens #6 and #10, which contain more hematite and specimen #10 that contains abnormal concentrations of jarosite and pyrite.  Iron Mask specimen #8 proved to be an outlier as well, having an epithermal formation temperature of only 155C.  Of the entire Iron Mask specimens that were analyzed, specimen #8 has the highest concentration of orthoclase and total clay.  Specimen #8 also contains significantly more molybdenum than the other specimens in the dataset, indicating the possibility of epithermal ore deposits and the potential for gold mineralization within the Iron Mask site.  The Iron Mask specimens that were analyzed predominately reside in the mesothermal temperature range of formation, between 200C to 300C. 

Figure 2 – Calculated formation pressure/temperature of the Iron Mask and DeMeules specimens

Geochemical Evaluation and Comparative Study of Cabochons Cut from the Rough

As previously mentioned, some rough Iron Mask specimens show what appears to be epoxy on the exterior of the surface.  The epoxy does not appear to have penetrated through the exterior of the stone and was likely a method used to preserve the turquoise for long storage, as it is well noted that some turquoise can discolor immediately after collecting it from being exposed to water vapor.  Certainly, it was known that the Iron Mask turquoise contained large amounts of sulfur, which could pose the problem of sulfuric acid generation and discoloration over time.  To verify that the epoxy is simply a surface coating and not from stabilization, a total of five cabochons were cut from the same specimen rough that were initially analyzed and reanalyzed for geochemical comparisons, particularly in the examination of aluminum and phosphorus.  Since turquoise is composed of aluminum and phosphorus, higher amounts of both compounds indicate a higher turquoise content.  Alternatively lower amounts of both generally indicate less turquoise and the potential for epoxy impregnation throughout the stone.  Epoxy is a carbon-based polymer and its presence can’t be detected using XRF analysis, as carbon is too light of an element for x-ray fluorescence.  As such the presence of epoxy generally lowers elemental concentrations and generates a lower total balance when the bulk chemical analysis is summed together.  If the epoxy is a surface coating only then the amount of aluminum and phosphorus will increase when the stone has been cut, effectively removing the exterior epoxy preservative.  Additionally, to examine the epoxy surface coating and its effects on a stone, a small piece of specimen number #9 was cut and placed in a jar of acetone for a duration of 48 hours and removed and dried.  It can be observed that the stone didn’t change color and only edges showed deterioration from where the epoxy was bound to the exterior of the stone. 

Figure 3 – Iron Mask specimen #9 after 48-hour immersion in acetone, note only edges fractured and epoxy came off as “chunks” instead of dissolved residue.

Five cabochons were cut from Iron Mask specimens #1, #9, #10, #2, and #3, to show the diversity of the turquoise and to verify if epoxy impregnated the interior of the stones.  Specimen #1 cab represents a higher mid-grade example with an intricate mineralized matrix, whereas specimen #9 cab is typical medium grade mine run with a sky-blue color that is representative of turquoise from the Iron Mask Mine.  Specimen #10 was chosen for follow-up analysis, as it contains the highest iron and sulfur concentration, coupled with high amounts of jarosite.  It produced an unusual pistachio green colored stone that was a bit softer than the other specimens that were cut.  Specimens #2 and #3 represent the higher-grade material for the Iron Mask, displaying intricate black spider webbing and a more saturated blue coloration.  Chemical analyses of the finished cabochons indeed show substantially higher concentrations of aluminum and phosphorus than the analysis of the rough.  Such an increase in both, coupled with higher element abundances confirm that the epoxy is only a surface treatment to prevent discoloration during storage and not invasive stabilization.  This noted increase in aluminum and phosphorus is more pronounced in specimen #10, as additional amounts of softer gypsum and jarosite were removed during the cutting and polishing process.  The removal of gypsum and softer mineralization upon cutting placed the Iron Mask turquoise in the same range of hardness as that of the comparable DeMeules turquoise.  The turquoise from both mines has a projected Moh’s hardness of 5 to 6.

Figure 4 – Iron Mask cabochons, cut from specimens #1, #9, #10, #2, and #3, from left to right and top to bottom.

Table 3 – Bulk and trace element chemistry of Iron Mask cabochons #1, #9, #10, #2, and #3

Wt. %	IM #1 Cab	IM #9 Cab	IM #10 Cab	IM #2 Cab	IM #3 Cab
SiO2	9.2113	3.3054	3.5785	4.4472	2.2280
Al2O3	25.9901	37.4446	14.4590	36.0959	38.4275
MgO	1.6671	1.6761	1.8780	1.6574	1.4170
CaO	0.2092	0.3932	0.2693	0.4833	0.0563
K2O	0.0150	0.0676	0.0749	0.1625	0.1020
Na2O	0.6873	0.8795	0.1213	0.8452	0.1201
P2O5	23.4419	28.9397	23.6920	27.8803	28.0994
TiO2	0.0167	0.2161	0.3648	0.0115	0.1879
FeO	0.9161	0.2653	1.9886	0.3767	0.0412
Fe2O3	7.1834	2.5209	22.5243	3.3579	0.4979
S	0.2668	0.1788	0.3960	0.1930	0.3311
Cl	0.0332	0.0053	0.0120	0.1432	0.0031
Ppm Wt.
Sr	594	872	203	234	214
Ba	2388	1436	1509	3145	950
Rb	2	5	2	8	2
Zr	6	18	6	48	4
Mo	4	7	5	10	3
V	150	138	211	34	65
Ni	43	29	57	30	25
Cu	49361	69418	46502	63889	60878
Zn	1347	384	160	377	3113
Cr	166	295	381	119	202
Pb	56	6	27	6	5
As	71	6	68	57	146
W	83	283	74	476	610
Sb	14	10	18	19	9
Sn	18	9	19	59	52
Ag	7	8	9	10	7
Bi	7	6	5	6	5
Nb	3	3	3	3	2
U	8	25	7	44	9
Th	3	3	2	4	2
Se	305	4	455	4	4
Li	0	0	0	1	0

Figure 5 – Iron Mask rough versus cabochons aluminum and phosphorus concentrations

Conclusions

Turquoise from the Iron Mask Mine is a rare long forgotten piece of New Mexico’s mining treasure, with a rich history that began with the ancient Aztecs and proceeded a gold rush that pronounced the Orogrande Mining regions claim to fame.  During the midcentury turquoise mining was proceeded by commercial exploration for iron and copper that created a disregard for turquoise, effectively yielding little Orogrande material for the gemstone trade, thus making turquoise from the region exceedingly rare.  Only limited amounts of turquoise were mined sporadically until 1980 when the mining operations completely ceased with no future plans of reopening.  Two types of turquoise are noted in the Orogrande Mining District, Iron Mask and DeMeules which the latter is probably more commonly available, considering the DeMeules mine is a gemstone site.  Turquoise from the Iron Mask mine shows an unusual amount of gypsum and jarosite, which if it was left in long term storage could potentially cause discoloration and disintegration from moisture reactions creating sulfuric acid.  The rough was coated with an exterior application of epoxy to prevent chemical reactions from moisture that could disintegrate the material, and the results of these findings indicate that it is not to be confused with invasive stabilization that penetrates the entire stone.  Geochemical analyses of both turquoise types show that DeMeules turquoise is formed from low pH solutions interacting with feldspar to produce kaolinite and limonite, whereas Iron Mask turquoise is produced from hydrothermal alteration of phosphorus rich shale to produce gypsum and evaporites.  Such findings are in good agreement with documented assessments proposed by the New Mexico Geological Survey.  

Acknowledgments

Special thanks to Mike Ryan and Philip Chambless for providing a detailed historical assessment of the Orogrande Mining region that can be found in Turquoise in America Part 1.  If you have not yet purchased Turquoise in America, I highly recommend obtaining your copy before it sells out.  If you are interested in having turquoise evaluated for origin or grade, West Texas Analytical Laboratory offers two options, which includes the origin XRF analysis that provides a comprehensive report of mineralogy, properties, origin, and grade, as well as a simplified one that provides only the chemical analysis.  The comprehensive origin XRF analysis contains a considerable amount of information for $65, it should be used to identify and grade seemingly valuable material.  The simpler XRF analysis is $30 and it should be used to identify if the stone is natural with no enhancements.  Sometimes, after acquiring the simpler analysis, one may wish to later acquire the comprehensive report with origin and grade.  As such, since the XRF analysis has already been ran, for another $35 to make up the balance to $65 the report can be upgraded to the comprehensive one at any time.  If you wish to submit samples, please contact West Texas Analytical Laboratory at 580-977-6951 or feel free to submit requests at wtalab.com.

As Mike Ryan would say “Be well, be happy and always wear your Iron Mask or DeMeules turquoise”