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Michael Cox's Photo Gallery

N5T-3FMCorderoite Hg2+3S2Cl2 , Cinnabar HgS , Goethite α-Fe3+O(OH) , Hematite Fe2O3 , Calomel [Hg2]2+Cl2 , Quartz SiO2

07051950016055019868626.jpg
McDermitt Mine, Opalite Mining District, Humboldt Co., Nevada, USA

Field of View: 4 mm

Rhyolite tuffaceous sediment replaced by quartz (white to colorless). A feature of the rock this specimen came from is banded stibnite in concentric layers up to many centimeters thick. In portions of the rock, such as this thumbnail sample, the stibnite has been replaced by hematite and goethite (lower right). Based on field observations of texture and inclusions, as well as the work of earlier researchers, especially McCormack (1986), it is evident that banded stibnite and quartz with minor pyrite was later oxidized in a series of events that included the early deposition of cinnabar and its subsequent alteration to corderoite and other redox products from the disproportionation of the cinnabar.

This photograph is of a small portion of a hand sample that was broken down to study the mineral paragenesis. This piece comes from rock that provided samples for both microprobe and pxrd analysis in order to verify the mineral identifications. One very interesting feature to the lower right is the deposition of red cinnabar within fractures, between cockade crystal faces, and between mammillary layers of what is now black goethite and dark-brown hematite. A layer extending over to the left side of the photograph contains massive orange-colored corderoite. To the left, the corderoite is prominent and it is also obvious that is a product of cinnabar alteration. See Dunning et al. (2019) for a more detailed description of the mineralogy, especially the write up regarding stibnite and its redox products.

Based on careful microscopic study and spot EDS/pxrd analyses, melanterite, senarmontite, cervantite, stibiconite, and valentinite also occur in the immediate vicinity, as well as the extremely rare mineral shakhovite, but this sample was not specifically tested or examined under high-magnification. Calomel occurs as very fine grain colorless to pale yellow masses. They are not obvious in the photo, but in the lab the calomel is readily identified by its very bright orange fluorescence under UV light, both long and short wave. The pictured thumbnail contains scattered grains of calomel throughout the matrix. Not in the photograph, lemon-yellow schuetteite also occurs, on a sample face that was a southeast-facing surfaces exposed to the weather. Although not in the photographed sample, adjacent areas of the rock contain terlinguaite, eglestonite, elemental mercury, and many unnamed mercury species that are under study. All in all, this assemblage of minerals indicates episodic precipitation from fluids where redox conditions must have been fluctuating significantly in order to bring this many species together in one small outcrop.

The photograph was taken with a Canon MP-E 65mm macro lens mounted to a Sony A7R DSLR camera. Lighting was provided by two super-bright LEDs, part of a lighting system designed, built, and sold by Swarf Systems of Sunnyvale, California (https://www.swarfsystems.com/). The "film speed" of the DSLR was ISO 100 and the exposure time was 1 second per frame. The lens and camera were mounted to a modified Leitz SM microscope stand with petrographic stage. The stage was raised approximately 1.4mm while taking 39 individual photographs that were then vertically composited using Zerene Stacker and the DMap mode with contrast set at 39%. The photo was cropped after stacking, but no other adjustments were made. Polarization film was used to align (plane polarize) the LED light in order to eliminate bright reflections. This technique does tend to somewhat saturate the colors, but this is useful for textural analysis.
Copyright: © Michael F. Cox      Photo ID: 1104378     Uploaded by: Michael Cox   View Count: 45   Approval status: Public galleries    Type: Photo - 4901 x 3274 pixels (16.0 Mpix)

GR5-P63Terlinguacreekite Hg2+3Cl2O2 , Kleinite (Hg2N)(Cl,SO4)·nH2O

00873900016021345486444.jpg
McDermitt Mine, Opalite Mining District, Humboldt Co., Nevada, USA

Field of View: 11.4 mm

Beautiful red-orange terlinguacreekite (Hg3Cl2O2) with minor yellow orange kleinite ((Hg2N)(Cl,SO4) · nH2O). Originally discovered at Terlingua, Texas, at McDermitt this phase is found in fluvial and lacustrine sandstone and wacke with conglomerate formed from lithic tuff. Kleinite is by far the dominant mineral, forming as coatings and fillings in fractures, pores, and cavities. Terlinguacreekite occurs rarely as scattered crystals in small solution cavities lines with colorless to white microcrystalline quartz. In one small area, pockets up to several centimeters in size contain predominantly terlinguacreekite on sugary gray quartz, with clear calomel (Hg2Cl2) as a coating on the crystals and minor kleinite. These minerals were verified with pxrd. Under UV light, both short and longwave, the calomel fluoresces an intense bright orange.

From Dunning et al, 2019, Baymin Journal, vol. 20(4), the composition of terlinguacreekite given here is based on Roberts et al. (2005, "Canadian Mineralogist," vol. 43, pp. 1055-1060), but recent Raman studies and work by Mark Cooper suggest that it is nitrogen in the structure instead of oxygen, as is the case for comancheite (Cooper et al., 2013, "Mineralogical Magazine, vol. 77, pp. 3217-3237). Bromine has been detected by EDS at concentrations less than 3%.

Fun fact, many mercury minerals darken in sunlight, like photographic film. Darkening can be very rapid when the mercury minerals contain halides such as chlorine, iodine, and bromine. The darkening is typically not reversible. Terlinguacreekite darkens in light, but if the exposure is not too long or intense, most terlinguacreekite will regain its color in a matter of days to months if stored away from any light.

To date, finds of excellent terlinguacreekite crystals have failed to yield material sufficiently free of twinning to allow for structural determination. Terlinguacreekite remains some what enigmatic, and, based on observations in the field, is clearly associated with kleinite, if not related to it. Microcrystalline presumed terlinguacreekite based on color and habit, often coats well-formed hexagonal crystals of yellow to yellow-orange kleinite.

This photo was taken with a prototype photomicrography stand built by Ted Hadley, Swarf Systems, of Sunnyvale, CA. The system, built on an Olympus BH microscope stand, is comprised of a Canon 5D Mark III camera coupled to a Mitutoyo 2x plan-apochromatic infinity objective. A Thor labs ITL-200 tube lens, an iris diaphragm, a linear polarization filter, and a bellows are between the camera and the objective. Lighting is provided by two opposing Nissin flash units with linear polarization filters. Approximately fifty individual photos are focus stacked using Zerene software. The resulting DMap was adjusted for contrast and color saturation because polarized light causes red to become oversaturated.
Copyright: © Michael F. Cox      Photo ID: 1098071     Uploaded by: Michael Cox   View Count: 11   Approval status: Public galleries    Type: Photo - 5184 x 3456 pixels (17.9 Mpix)

LAY-30RTerlinguaite [Hg3]4+Hg2+Cl2O2 , Quartz SiO2 , Goethite α-Fe3+O(OH)

09915790016021305863392.jpg
McDermitt Mine, Opalite Mining District, Humboldt Co., Nevada, USA

Field of View: 2.5 mm

INVASION OF THE QUARTZ SNATCHERS

Terlinguaite (Hg₂ClO) (yellow) determined by pxrd on and with quartz. The quartz crystals are stained brown with iron oxide, possibly hematite. In the center of the photograph a cluster of quartz crystals, some double-terminated, is partially covered with silica tubules (visual identification) that are, in turn, coated with black iridescent goethite. There is a highly-reflective colorless mineral at the center of the photograph that has not yet been investigated, but appears to be a grainy form of silica based on optical properties under polarized light microscopy.

The sample comes from a location of redox that followed the deposition of cinnabar after the deposition of banded massive quartz and stibnite in fractures, voids, and as a replacement of lacustrine and fluvial tuffaceous (clastic rhyolite tuff) sediments ranging in grain size from mudstones to gravel conglomerates.

The photo was taken with a Canon 5D Mark-III camera with MP-E 60mm macro lens and two opposed Nissin flash units. Focus stacking with Zerene Stacker. Post-processed for exposure and contrast.
Copyright: © Michael F. Cox      Photo ID: 1098064     Uploaded by: Michael Cox   View Count: 8   Approval status: Public galleries    Type: Photo - 2179 x 2557 pixels (5.6 Mpix)

Cinnabar (HgS) replacement cut by fault

01641810016013129359485.jpg
Cahill Mine, Poverty Peak Mining District, Humboldt Co., Nevada, USA

OLYMPUS DIGITAL CAMERA E-PL1 with built-in flash, horizontal field of view is about 1-meter.

Rich cinnabar (HgS) ore replacing dolostone and cut by a later bedding-plane fault (slip). Photo post-processed with Microsoft photo editor for exposure and contrast.

According to Nevada Bureau of Mines and Geology summary report for the Poverty Peak Mining District, report number 3690-0005, page 122, 1985 (downloaded 09/2020 from URL: http://data.nbmg.unr.edu/Public/MiningDistricts/3690/36900005.pdf) the mercury deposits occur in interbedded limestone, dolomite, and quartzite of Pennsylvanian-Permian age. There is local silicification, and the rocks are cut by calcite and quartz veins. The cinnabar ore is unusually high-grade and occurs as stockworks with quartz and calcite veins and large replacement ore bodies primarily in carbonate rocks. In the Cahill mine, cinnabar in limy quartzite and recrystallized dolomite is localized beneath a narrow fault gouge zone more or less parallel to bedding, which dips variably and steeply toward the northwest.
Copyright: © Michael F. Cox      Photo ID: 1096651     Uploaded by: Michael Cox   View Count: 15   Approval status: Public galleries    Type: Photo - 1280 x 960 pixels (1.2 Mpix)

QT2-KDKEglestonite [Hg2]2+3OCl3(OH) , Cinnabar HgS , Dolostone

05391870016013100541929.jpg
Cahill Mine, Poverty Peak Mining District, Humboldt Co., Nevada, USA

Field of View: 21 cm

OLYMPUS DIGITAL CAMERA E-PL1 with built-in flash, two photos stitched with Microsoft Image Compositing Editor.

Red crystalline cinnabar, HgS, filling voids and replacing sandy dolomite rock (dolostone). Yellow and greenish-yellow eglestonite, [Hg2]2+3OCl3(OH) replacing cinnabar along thin fractures. Although hard to discern in the photograph, the thin fractures with eglestonite are perpendicular to the layer of concentrated cinnabar replacement. Other photographs from the area show the concentration of cinnabar under the clayey fault gouge of a bedding plane fault, and the eglestonite occurs along fractures that are more or less vertical and tangent to the strike of the main fault. The eglestoite is powdery and rapidly turns dark olive-green when exposed to sunlight. Photomicrographs for this location show the cinnabar and eglestonite replacement in detail.
Copyright: © Michael F. Cox      Photo ID: 1096647     Uploaded by: Michael Cox   View Count: 21   Approval status: Public galleries    Type: Photo - 1874 x 850 pixels (1.6 Mpix)

Bedding plane fault with red cinnabar and yellow-green eglestonite

02624930016012642095439.jpg
Cahill Mine, Poverty Peak Mining District, Humboldt Co., Nevada, USA

Bedding plane fault with cinnabar (HgS) infilling and replacement along brecciated layer below clayey iron-stained fault gouge. Not evident in the photo is the replacement of red cinnabar (HgS) by yellow-green eglestonite ([Hg2]2+3OCl3(OH)) along secondary thin vertical fractures. The replacement of cinnabar by eglestonite is evident in photomicrographs of cinnabar and eglestonite from this location. The eglestonite is most concentrated away from the main fault and the highest concentration of cinnabar.

It is interesting that cinnabar is most concentrated immediately adjacent to the clayey fault gouge, while the eglestonite is more pronounced away from the fault gouge. The reasons are not known, but two possibilities are the fault gouge formed a physical barrier that channeled mercury rich fluids and the fault gouge chemistry somehow encouraged the precipitation of HgS. Slippage along bedding planes, apparently before and during HgS deposition, is evident in the mine. Note the iron-stained clayey slickenside surfaces above the main zone of cinnabar deposition. Cinnabar slickensides also occur under the bedding-plane fault, but are not obvious in the photograph.

The host rock is sandy dolomite that has been brecciated. Water seeping along open fractures has caused oxidation and weathering. Note the iron staining. The damp spots are from washing down the face for the photograph, but out of view to the right, the bedding-plane fault weeps water after the very brief winter rainy season.

Estwing rock pick provides scale. Photo view is about 1.5 meters across.

OLYMPUS DIGITAL CAMERA EPL-1 and built-in flash.
Copyright: © Michael F. Cox      Photo ID: 1096414     Uploaded by: Michael Cox   View Count: 39   Approval status: Public galleries    Type: Photo - 2310 x 1379 pixels (3.2 Mpix)

41F-5HECinnabar HgS , Eglestonite [Hg2]2+3OCl3(OH)

08446910016012642528162.jpg
Cahill Mine, Poverty Peak Mining District, Humboldt Co., Nevada, USA

Field of View: 4.5 mm

Cinnabar (red), eglestonite (yellow), and unidentified phase (tan coating on HgS). The cinnabar from this mine is well known, as is eglestonite. In this case, the eglestonite was confirmed with Raman spectroscopy and xrd under direction of Dr. Elise Knittle, School of Earth and Planetary Sciences, University of California, Santa Cruz. The tan alteration product on the cinnabar is reported by some to be eglestonite as well, but this is in question, as it properties are distinct from the eglestonite that it occurs with. Further study is needed. The tan mineral texture is parallel to cleavages and crystal faces of the cinnabar, suggesting it is an alteration product from the cinnabar and not just a secondary non-mercury mineral that invaded along fractures and partings.

The cinnabar from the Cahill mine occurs mainly as fracture fillings and replacement bodies along poorly-developed bedding-plane faults in the undivided Permian Havallah (?) and Pumpernickel (?) formations of sandstone, sandy dolomite, and carbonate rocks. The rich ore in the Cahill mine replaced carbonate rock. (Wilden, 1964, p. 103). The photographer, Cox, has observed that some of the rocks in the mine have been silicified and could be called quartzite.

The photographer has observed that HgS redox minerals occur along fractures that apparently allowed a secondary wave of hydrothermal alteration to disproportionate cinnabar. The main alteration product is yellow eglestonite that rapidly turns green and then dark green when exposed to sunlight. See additional locality photograph posted by Cox.

Photo taken with Sony A7R camera attached to phototube of a Leitz Orthoplan microscope fitted with Ultropak 50W-Halogen coaxial incident illumination system with 3.8x objective. 51 separate images at various focal depths stacked using CombineZP(tm) software by Alan Hadley and cropped to size to eliminate stacking errors along the edge of the photograph.
Copyright: © Michael F. Cox      Photo ID: 1096399     Uploaded by: Michael Cox   View Count: 17   Approval status: Public galleries    Type: Photo - 3450 x 2277 pixels (7.9 Mpix)

91X-UW4Terlinguaite [Hg3]4+Hg2+Cl2O2 , Goethite α-Fe3+O(OH) , Quartz SiO2 , Cinnabar HgS , Corderoite Hg2+3S2Cl2 , Shakhovite [Hg2]2+Hg2+2[Sb3+O3](OH)3

03376890015919082176887.jpg
McDermitt Mine, Opalite Mining District, Humboldt Co., Nevada, USA

Field of View: 4 mm

Terlinguaite and iridescent goethite on quartz in a matrix of silicified tuffaceous sediment. Minor red colloidal cinnabar with an admixture of corderoite (up to 25% or so) occurs scattered in the matrix, a thin band is visible at the lower left. The goethite displays a typical iridescence and it, as well as the brown iron staining, might be from the decomposition of pyrite during mineralization of the mercury mine deposit.

This sample is a small pocket approximately 2-cm in size recovered from an exposure of veined stibnite and cinnabar in silicified tuffaceous rock. The matrix is rich in massive stibnite. The cinnabar , goethite, and quartz are typical. The quartz crystals are distinct and are often enveloped by black silica tubes and presumed goethite, based on luster, iridescence, and past PXRD identification at this location. Where the quartz appears to be black, brown, or red, it is because of inclusions and the substrate. Goethite and silica tubes are most abundant where terlinguaite also occurs. Corderoite is presumed based on the fact it occurs in an intimate mixture with cinnabar at this deposit, and also because matrix not shown contains microscopic corderoite crystals.

The terlinguaite and shakhovite were confirmed by Gail Dunning, well known expert on mercury minerals and locations. Gail was assisted by Anthony Kampf, who performed the PXRD. AT the left center side of the photo is a flat-lying striated crystal that is not tapered. This might be shakhovite, a mineral also found in this small pocket.

Goethite is sometimes included in the quartz, but mostly coats the quartz. The yellow-green terlinguaite mostly covers the goethite and silica tubes, but the later sometimes coat the terlinguaite or are included in the terlinguaite. This, and the assemblage of secondary oxide minerals formed by the redox of other minerals, for example goethite after pyrite, suggest oxidation during deposition. McCormack (1986) believed meteoric water mixing probably supplied limited oxygen during the hydrothermal activity, but also believed that most of the oxidation products at the deposit are supergene and formed much later from ordinary weathering processes. The goethite in this specimen, being included in quartz that is, in turn, under terlinguaite, points to oxidation during the mineral precipitation.

This pocket was found in vuggy banded stibnite and quartz veining, with post-deposition but coeval dissolution and then in-filling of pores, voids, and fractures with massive cinnabar and corderoite, and then subsequent alteration to secondary mercury minerals, including those shown here and others not shown, such as calomel, montroydite, and a half-dozen unnamed mercury minerals that are in process for characterization and naming. The silicified tuffaceous sandstone matrix is comprised of grains of locally-reworked (fluvial and lacustrine) peralkaline rhyolite ash dating to about 16.39 ± 0.02 Ma (n = 3) (Henry et al., 2017), the main eruption of the McDermitt caldera. Antimony, mercury, and other trace elements in hydrothermal fluids invaded the volcanic rocks and sediments very soon after the first ring fractures formed around the developing caldera collapse. From the research of a significant body of professionals and academics, the caldera geology and mineral deposits are well defined.

Henry et al. of Stanford University published a fabulous map and description of the McDermitt caldera and rocks. It can be downloaded online. As of June, 2017, the URL for the map is: https://pubs.nbmg.unr.edu/Prel-geol-McDermitt-caldera-p/of2016-01.htm
Copyright: © Michael F. Cox      Photo ID: 1058211     Uploaded by: Michael Cox   View Count: 24   Approval status: Public galleries    Type: Photo - 5184 x 3456 pixels (17.9 Mpix)

Enriqueta Mine Workings - U.S.G.S. Professional Paper 360 (1964)

09508040015903405511496.jpg
Enriquita Mine, New Almaden, New Almaden Mining District, Santa Cruz Mountains, Santa Clara Co., California, USA

Looking down on the Enriqueta mine area in GoogleEarth(tm) with workings map, Plate 96 from Bailey and Everhart, 1964, U.S.G.S. Professional Paper 360, superimposed on the satellite photography. The placemark pins are the principal mine tunnel portals and shaft collars, field verified by Michael Cox, 1984-2020. Cox is a founding Board member of the New Almaden Quicksilver County Park Association and from 1984-1986 directed a two-year project to close off the former mine entrances. None of these openings are accessible in 2020, but are shown here to document the locations for historical purposes.

Note that the Enriqueta is the proper name of the mine as christened (blessed) in 1859, but today most maps and publications refer to it in the Spanish diminutive, Enriquita, because the mine was named for Henry Laurencel's daughter. Laurencel was part owner of the nearby (to the north) Guadalupe mine and had many land and financial interests in the New Almaden mining district. The land grant upon which the mine was located, Rancho Cañada de los Capitancillos, was a Mexican-era 1842 land grant to Justo Larios. Larios sold the grant to Grove C. Cook, founder of the Santa Clara Mining Company of Baltimore and operators of the Guadalupe mine. The Rancho was soon acquired by the Santa Clara Mining Company (1/4) and Charles Fossat purchased the southern portion in 1852, after Cook died.

Charles Fossat and the Enriqueta mine would become world famous when Fossat et al. joined forces with the might of the U.S. Federal government in a successful claim against the title of the New Almaden mine, owned by Barron, Forbes, and Company, directors of the New Almaden Company. The reduction furnaces at New Almaden were on Rancho San Vincente, a Mexican land grant to the Berreyesa family (also spelled Berreyessa, descendants of Berrelleza). The mine works were on the Rancho de Los Capitancillos. The "Fossat claimants," eventually organizing into the Quicksilver Mining Company of New York, litigated the New Almaden Company for over thirteen years. With major U.S. government assistance, the New Almaden Company finally "settled" the claim in 1863, selling the mine to QSMC for $1.75-million dollars. Litigation had cost over $550-thousand dollars.

The case of the New Almaden mine is considered one of the longest and most complicated cases heard by the district and U.S. Supreme Courts. The court records are a treasure trove of perspective into life both mundane and exciting on the stage of the closing years of Mexican rule and the opening years of the eventual U.S. State of California. There is much information online. The reader's attention is called to Bailey and Everhart (1964) in particular for geological and mining details, including the history of the development of the mines.

Note that Google(tm) allows use of the GoogleEarth(tm) image for non-commercial use provided proper attribution is made to Google. You may find more information at this link: https://www.google.com/permissions/geoguidelines/attr-guide/, or by searching the Internet for "permissions - GoogleEarth," if the link no longer works.
Copyright: © Google (air photo) and Michael F. Cox (pin locatio      Photo ID: 1054034     Uploaded by: Michael Cox   View Count: 45   Approval status: Public galleries    Type: Photo - 4800 x 2623 pixels (12.6 Mpix)

Principle tunnel portals and shaft collars of Enriqueta Mine

08185860015903402571335.jpg
Enriquita Mine, New Almaden, New Almaden Mining District, Santa Cruz Mountains, Santa Clara Co., California, USA

Oblique view looking southeast at Enriqueta mine area in GoogleEarth(tm) showing principal mine tunnel portals and shaft collars as shown on Plates 1 and 96 from Bailey and Everhart, 1964, U.S.G.S. Professional Paper 360, field verified by Michael Cox, 1984-2020. Cox is a founding Board member of the New Almaden Quicksilver County Park Association and from 1984-1986 directed a two-year project to close off the former mine entrances. None of these openings are accessible in 2020, but are shown here to document the locations for historical purposes.

Note that the Enriqueta is the proper name of the mine as christened (blessed) in 1859, but today most maps and publications refer to it in the Spanish diminutive, Enriquita, because the mine was named for Henry Laurencel's daughter. Laurencel was part owner of the nearby (to the north) Guadalupe mine and had many land and financial interests in the New Almaden mining district. The land grant upon which the mine was located, Rancho Cañada de los Capitancillos, was a Mexican-era 1842 land grant to Justo Larios. Larios sold the grant to Grove C. Cook, founder of the Santa Clara Mining Company of Baltimore and operators of the Guadalupe mine. The Rancho was soon acquired by the Santa Clara Mining Company (1/4) and Charles Fossat purchased the southern portion in 1852, after Cook died.

Charles Fossat and the Enriqueta mine would become world famous when Fossat et al. joined forces with the might of the U.S. Federal government in a successful claim against the title of the New Almaden mine, owned by Barron, Forbes, and Company, directors of the New Almaden Company. The reduction furnaces at New Almaden were on Rancho San Vincente, a Mexican land grant to the Berreyesa family (also spelled Berreyessa, descendants of Berrelleza). The mine works were on the Rancho de Los Capitancillos. The "Fossat claimants," eventually organizing into the Quicksilver Mining Company of New York, litigated the New Almaden Company for over thirteen years. With major U.S. government assistance, the New Almaden Company finally "settled" the claim in 1863, selling the mine to QSMC for $1.75-million dollars. Litigation had cost over $550-thousand dollars.

The case of the New Almaden mine is considered one of the longest and most complicated cases heard by the district and U.S. Supreme Courts. The court records are a treasure trove of perspective into life both mundane and exciting on the stage of the closing years of Mexican rule and the opening years of the eventual U.S. State of California. There is much information online. The reader's attention is called to Bailey and Everhart (1964) in particular for geological and mining details, including the history of the development of the mines.

Note that Google(tm) allows use of the GoogleEarth(tm) image for non-commercial use provided proper attribution is made to Google. You may find more information at this link: https://www.google.com/permissions/geoguidelines/attr-guide/, or by searching the Internet for "permissions - GoogleEarth," if the link no longer works.
Copyright: © Google (air photo) and Michael F. Cox (pin locatio      Photo ID: 1054033     Uploaded by: Michael Cox   View Count: 36   Approval status: Public galleries    Type: Photo - 4800 x 2623 pixels (12.6 Mpix)

Triple-distillation still for purifying mercury at Almadén Mercury Museum

08612370015860163004722.jpg
Almadén Mine, Almadén, Almadén mining district, Ciudad Real, Castile-La Mancha, Spain

Triple-distillation unit. Railing is approximately 4-meters wide.

According to the museum description, this device was installed at the mines in 1980 in response to customer requests for triple-distilled mercury of a purity of 99.999%. Triple-distilled Hg is typically requested when making specialty mercury compounds and chemical reagents. The triple-still device is used to carefully heat the mercury and run it through three cycles of vaporization and condensation. The normal single-condensed mercury (called Prime Virgin) from Almadén is said to have been 99.9% pure. I am not sure if this plant used vacuum assistance, but some do, typically to help remove volatile contaminants and to assist with vaporization of the mercury.

There are other methods to purify mercury to various grades, including acid-washing, filtration, and electrolytic purification, but triple distillation is the most common and results in American Chemical Society (ACS) reagent-grade (99.9995%) mercury that commands a premium price. Triple-distilled mercury is used in applications where minor impurities in the mercury would interfere with subsequent use. The prime virgin mercury at most mercury mines was 99.9% pure, but some had trouble with impurities and their prime-virgin ran at 99.5%. Impurity of 0.1% to 0.5% can be significant if doing trace-element experiments. For example, each gram of prime-virgin mercury could respectively contain 1,000 to 5,000 micrograms of unknown impurities.

Mindat.org Photo of the Day - 23rd Aug 2020
Copyright: © Michael F. Cox      Photo ID: 1041273     Uploaded by: Michael Cox   View Count: 250   Approval status: Public galleries    Type: Photo - 4032 x 3024 pixels (12.2 Mpix)

JED-0NUCorderoite Hg2+3S2Cl2 , Cinnabar HgS , Quartz SiO2

04712190015823702665682.jpg
McDermitt Mine, Opalite Mining District, Humboldt Co., Nevada, USA

Field of View: 2.350 mm

Honey-colored massive corderoite (Hg3S2Cl2) replacing cinnabar (HgS). This sample was given to Gail Dunning, who secured identification via pxrd. There might be an unidentified (untested) mercury phase in the filling of the fracture between the two areas of massive cinnabar and corderoite. The matrix is light-grey Miocene rhyolite ash-flow tuff (Tuff of Long Ridge, a.k.a. McDermitt Tuff) somewhat reworked by surface water.

As summarized in Dunning et al. (2019), at the McDermitt mine corderoite is unusually abundant (~25% of the ore: McCormack 2000). The mineral was determined to be a hypogene replacement of cinnabar, sometimes volume-for-volume. Its formation is likely due to a high activity of chloride in hydrothermal solutions (McCormack 1986). McCormack also believes the majority of the host rock silicification occurred after the cinnabar partially altered to corderoite, thereby protecting the corderoite from dissolution during subsequent waning hydrothermal activity, oxidation, and weathering.

Corderoite was encountered in early drill-hole exploration of the McDermitt mine area. Dr. Eugene Foord worked out the mineral identity in 1973. The results were published in 1974, after which the mineral was discovered in several other mercury deposits around the world. At first, based on drill-hole data, researchers thought the deposit was hot spring mercury deposition in surface and near-surface siliceous sinter and tuffaceous sediment in a caldera lake. As the open pit mine progressed in the 1980s, it became obvious that the deposit was due to hydrothermal activity that occurred at some depth below the surface. See Dunning et al. (2019) for more information.

Approximately 25 photographs stacked with Zerene(tm) software. Sony A7R camera coupled to the triocular pol-tube of a 1980s Leitz Orthoplan research microscope with an Ultropak coaxial-light illumination and objective system. 50 W halogen light. The incident light is polarized and the return light is passed through a second polarizer (crossed-Nicols) before reaching the camera sensor. This eliminates glare. 3.8x Ultropak objective and intermediate lens for finite 210mm tube length.
Copyright: © Michael F. Cox      Photo ID: 1032233     Uploaded by: Michael Cox   View Count: 28   Approval status: Public galleries    Type: Photo - 7360 x 4912 pixels (36.2 Mpix)

9UY-CYYCalc-silicate rock, Bitumen

03761180015759080204966.jpg
New Almaden Mine, New Almaden, New Almaden Mining District, Santa Cruz Mountains, Santa Clara Co., California, USA

Field of View: 6 inches

Breccia, Tertiary Silica-carbonate rock (TSc). Identified visually based on mineralogy, texture, and known locality. TSc is an alteration product of Jurassic-Cretaceous serpentinite (JSp), which, in turn, is an alteration product of a Jurassic ocean plate and upper-mantle rock, which, in general can range from an intermediate basalt to a ultramafic peridotite, with many mafic and ultramafic rocks in between.

Specimen is 5-inches across along top cut face. Cement is finely divided quartz and what appears to be bitumen, a heavy hydrocarbon residual, like asphalt. Small grains of cinnabar are scattered about in the clasts and the matrix. It is easy to see many generations of fracturing, from the earliest iron-stained hairline cracks in the JSp protolith to the thicker bluish-white massive quartz that is filling latest stage fractures. Even these late-stage quartz veinlets are broken up, as one can see pieces of the veins in the breccia. Under the microscope at 30x magnification, one can see scattered tiny blebs of bright red cinnabar in both the clasts and the matrix.

Silica-carbonate rock description compiled from Bailey and Everhart, 1964, USGS Professional Paper 360:

•Derived from serpentine by hydrothermal alteration.

•Composed principally of silica (SiO2) and a carbonate, generally ferroan magnesite (Mg,Fe)CO3).

•In the New Almaden District, chalcedony and opal are so uncommon they can be disregarded in a general description.

•Host rock for the more productive bodies of quicksilver ore. [Cox note: and with higher mean Hg concentration than any other rock types in the mining area.]

•Always restricted to serpentinite bodies, either as replacement rims at the edges or complete replacement where the serpentinite was thin and sheared.

•Pseudomorphic textures inherited from serpentine are typical and recognizable, including the sheared structure of serpentinite

•Typically contains residual unaltered minute crystals of chromite (FeCr2O4) or picotite ((Fe,Mg)(Al,Cr)2O4) [Cox note: International Mineralogical Association rejected name, proper name is Mg- and/or Cr- bearing hercynite (Fe2+Al2O4)].

•Weathering removes ferroan magnesite, leaving only hydrated ferric oxides and silica. [Cox note: blebs of Cr-bearing clay (green) is common weathering artifact.]

•If silica content is low, the rock weathers to an ocherous soil containing only a few siliceous fragments.

•Weathered and ocherous rock often has siliceous skeletons of bastite [(D3[Si2O5](OH)4 D= Mg, Fe, Ni, Mn, Al, Zn) pseudomorphs [serpentine-group minerals after enstatite (Mg2Si2O6)] or vaguely lenticular textures discernible in places, and nearly everywhere the ocher will yield chromite or picotite[Mg/Cr-bearing hercynite] if panned.

[Cox note: the general chemical oxide composition of TSc from this mine does not vary significantly between TSc without cinnabar and TSc with abundant cinnabar. This suggests that the TSc is an older and more regional rock that later served to host very localized hydrothermal fluids that carried cinnabar into the rock, mainly along fractures and with limited replacement of the host rock.]
Copyright: © Michael F. Cox      Photo ID: 1017594     Uploaded by: Michael Cox   View Count: 25   Approval status: Public galleries    Type: Photo - 4032 x 3024 pixels (12.2 Mpix)

QNC-FGRQuartz (Var: Chalcedony) SiO2 , Cinnabar HgS , Corderoite Hg2+3S2Cl2

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McDermitt Mine, Opalite Mining District, Humboldt Co., Nevada, USA

Dimensions: 16 cm x 10 cm x 4 cm
Largest Crystal Size: 1 mm

Bulk rock sample. Massive cinnabar and corderoite filling pore space and fractures in silicified tuffaceous sediment derived from rhyolite tuff. The tuff is the McDermitt Tuff of Henry et al. (2017) (called the Tuff of Long Ridge by Benson (2018)). The tuff is caldera fill erupted during the collapse of the McDermitt caldera at about 16.4 mya (Henry et al. 2017, Benson 2018).

The rock in the photo is likely the volcanic wacke (mudflow) described by Giraud (1986), a rock made up of fluvially-reworked eruptive rhyolite ash and ejecta. This rock is part of a thick sequence of tuffaceous caldera-fill sediments that were invaded by hydrothermal fluids during and shortly after the caldera collapse. The fluids, in several episodes, deposited mainly quartz, stibnite, and cinnabar, but also caused pervasive alteration (argillization) of the tuffaceous sediments, converting upper layers to clay beds, possibly along the top of a fluctuating saturated zone.

At some point during the ore deposition, and prior to final silicification and argillization, reducing conditions in a chlorine-rich environment resulted in about 25% of the cinnabar being altered to massive brick-red to brown corderoite (Hg3S2Cl2). After this event, silica deposition (chalcedony) returned and deposited silica largely as pore and fracture filling, creating "agate beds" in lenses and layers conformable to the parent rock bedding and zones of higher permeability. Mercury minerals were also oxidized during this later-stage event, as well as iron sulfides, forming gypsum, goethite, and hematite. Post-hydrothermal weathering has also created these minerals as supergene products, but when this is the case, the minerals are the last to be deposited in the paragenetic sequence and are not covered or coated by any other mineral.

The rock in the photo is lying sideways. In-situ, it would be rotated 90-degrees and the right side would be the top or up position. The right side is a clayey layer, below which fluids deposited HgS in fractures and pore spaces in the volcanic wacke parent rock. The silicification is often so pervasive the rock is recrystallized to an agate-like material. The parent rock textures are somewhat obscured, and in some places largely erased by silica crystallization.

The cinnabar appears to have been commonly deposited in colloidal form in open spaces, such as pores, vesicles, and fractures. Some of the cinnabar is more coarsely crystalline, in massive aggregations with individual crystals of perhaps a mm or so. More coarsely crystalline cinnabar seems to be found in near vertical fractures that cut the parent rock, and also where there are dome-like structures in the bedding.

The red cinnabar and corderoite ore rapidly turns grey in the sun, perhaps because of the corderoite and/or chlorine content. Some samples can take months or even a year or so to darken. Other samples can turn grey in a matter of minutes in strong sunlight.

Photo taken with Olympus EPL-1 camera with Zukio 14-42 mm lens and built-in flash, full automatic setting.
Copyright: © Michael F. Cox      Photo ID: 1012321     Uploaded by: Michael Cox   View Count: 48   Approval status: Public galleries    Type: Photo - 1103 x 735 pixels (0.8 Mpix)

A70-730Corderoite Hg2+3S2Cl2 , Kenhsuite Hg2+3S2Cl2

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San Francisco mine, El Hembrar, Chóvar, Castellón, Valencian Community, Spain

Field of View: 1.1 mm
Largest Crystal Size: 0.3 mm

Mottled light brown corderoite crystal on black unidentified mineral (probably Mn or Fe oxide-hydroxide) and surrounded by smaller blocky corderoite crystals and acicular crystals of kenhsuite. The orange phase on the crystals is not identified (probably iron hydroxide such as limonite), as well as the blue-green phase (probably malachite). Corderoite from this location has been confirmed by pxrd. Kenhsuite is the gamma (y) polymorph of Hg3S2Cl2. Photo taken with Leitz Orthoplan microscope fitted with Leitz Ultropak 6.5x objective and Sony A7R camera mounted to triocular phototube. Illumination was provided by a 50W halogen bulb in the standard illumination housing. 158 individual images were stacked with Zerene software to produce the final image, which was then processed for color accuracy and to remove lighting and dust artifacts.
Photo ID: 1012200     Uploaded by: Michael Cox   View Count: 51   Approval status: Public galleries    Type: Photo - 7360 x 4912 pixels (36.2 Mpix)

Y3T-1XRShakhovite [Hg2]2+Hg2+2[Sb3+O3](OH)3 , Goethite α-Fe3+O(OH) , Quartz (Var: Chalcedony) SiO2

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McDermitt Mine, Opalite Mining District, Humboldt Co., Nevada, USA

Field of View: 1175 μm
Largest Crystal Size: 600 μm

Shakhovite, (Hg-Hg)2+2Sb5+O3(OH)3

From Dunning et al., 2019, p. 72: "This very rare mercury antimony oxide, verified by PXRD methods, was discovered in samples from a cinnabar-stibnite contact zone. Individual monoclinic crystals with an adamantine luster occur on quartz coated with an iron oxide(?). The crystals are emerald green with striations along the c axis. Associated with the shakhovite are abundant light brown rosettes of another similar phase, (Hg-Hg)2+2Sb5+4O12, MCDUK-19, currently under study."

The shakhovite was found by the photographer in a tiny vug lined with silica (quartz and chalcedony) coated with goethite. Goethite-coated microscopic silica tubules cover the quartz and other mineral surfaces, and, in turn, are sometimes embedded in or covered by quartz crystals. This is a characteristic feature of the vugs in the discovery location and suggests that oxidation occurred at least toward the end of the hydrothermal mineral deposition if not during the main episode.

The PXRD analysis was performed by Anthony Kampf, and is the first confirmed discovery of shakhovite outside of Europe and Central Asia. Mineral collectors are encouraged to investigate other stibnite-cinnabar contacts in zones of hydrothermal alteration where oxidation products of both mercury and antimony are found. At McDermitt, shakhovite is difficult to distinguish from terlinguaite without characterization by a determinative scientific instrument.

Dunning et al. (2019, p. 37) describe the shakhovite location as follows: a ". . .small but highly productive outcrop yielded exceptional examples of many minerals, including rare mercury and antimony minerals, such as shakhovite, valentinite, and tiny but visible crystals of terlinguaite. The minerals occur in dark-grey silicified zones in tuffaceous rock. The rock is a mixture of mainly fluvial and lacustrine deposits of reworked ignimbrite. Thin laminae of finer, silty material is interbedded with coarser tuff containing lithic fragments of yet more tuff. Mineralization occurs as pore-filling and crystallization in flattened pockets conformable to the bedding structures of the rock."

Dunning et al. (2019, p. 38) describe the shakhovite mineral find as follows: "Very rare shakhovite was identified within several quartz-lined cavities attached to crystals coated with iron oxide. The shakhovite is greenish-yellow and is prismatic in habit, with striation parallel to the c-axis."

The unknown yellow mineral occurring in the small vug with the shakhovite was given the designation McDUK-23 (McDermitt Unknown 23) by Dunning et al., and they state (p. 103): "This unknown mercury-bearing phase was first noted in samples from Area 4, where rich samples of cinnabar, stibnite, and pyrite were recovered. A region of this site has been subjected to local oxidation by fluids, resulting in several new mercury phases, this being one of them. This phase is currently under study in Spain. Refinement of the structure is essentially complete at R=4.6% in Fmmm and supports simple Hg3S2Cl2 formula."
Copyright: © Michael F. Cox      Photo ID: 1003780     Uploaded by: Michael Cox   View Count: 62   Approval status: Public galleries    Type: Photo - 4090 x 2729 pixels (11.2 Mpix)

TCN-QM5Corderoite Hg2+3S2Cl2 , Quartz (Var: Chalcedony) SiO2 , Cinnabar HgS

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McDermitt Mine, Opalite Mining District, Humboldt Co., Nevada, USA

Field of View: 1.2 mm

Corderoite crystal (dark brown) with {011} edge modifications and unknown number 3 (yellow-cream, Hg2+3S2(SO4,MoO4)) on chalcedony lining a tiny pocket in "opalite." Opalite is a local name for tuffaceous sediments that were buried, lithified, and later invaded by epithermal solutions rich in mercury and silica, depositing cinnabar, corderoite, unknowns, and chalcedony. The corderoite is an alteration product of cinnabar. The following description of the probable sequence of formation is from Dunning et al., 2019, pp. 31-32:

1 Introduction of mercury sulfide solutions within the horizontal layers of host rock. Possible deposition of pyrite as well, although the pyrite is greater in extent than the mineral deposit (Speer, 1977) and may be an older mineral related to the ignimbrite host rocks.

2 Solutions rich in chloride invaded this host rock and partially altered the cinnabar to massive corderoite. Clay minerals are also formed.

3 Silica-rich solutions invaded the mercury-rich rock, with the formation of many cavities and vugs.

4 Specific ion-rich solutions, possibly derived from the initial corderoite-forming fluids formed (phase 1) a mercury-sulfide-molybdate, (phase 2) a mercury-sulfide-sulfate/molybdate, and (phase 3) cubic crystals showing edge modified edges {011} of corderoite following sequence (2). No time relationship was found between (1) and (2); the cubic corderoite crystals were found to be later than phase (2). Phase (2) shows a hexagonal outline with a dark-brown core. Minute corderoite crystals were identified coating these prisms.

5 Within small quartz-lined cavities/vugs in the corderoite-rich breccia, minute colorless acicular crystals had formed, identified as kenhsuite. These crystals formed on the prior quartz crystals. Again, no time relationship was found between the kenhsuite and the phases described under sequence 4.

6 Supergene oxidation and weathering of the deposit. Jarosite, hematite, limonite, and extensive clay minerals formed, although some of the jarosite may be related to event 4 or 5.

Photo taken with halogen fiber-optic lighting, Nikon 5x Apochromatic objective, Canon EOS T3i camera, and custom photomicography stand built by Swarf Systems, Ted A. Hadley, Sunnyvale, CA.
Copyright: © Michael F. Cox      Photo ID: 983981     Uploaded by: Michael Cox   View Count: 65   Approval status: Public galleries    Type: Photo - 1834 x 1223 pixels (2.2 Mpix)

AK7-QVKCalomel [Hg2]2+Cl2 , Quartz SiO2 , Cinnabar HgS , Quartz (Var: Chalcedony) SiO2 , Tuffaceous-sedimentary-rock

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McDermitt Mine, Opalite Mining District, Humboldt Co., Nevada, USA

Field of View: 10 mm
Largest Crystal Size: 0.1 mm

Tetragonal calomel crystal on quartz druse in small pocket in silicified tuff. Well-formed calomel crystals are scant from this deposit. Smaller crystals are just to the left and a slightly larger mass to the right. The calomel fluoresces a brilliant poster-orange under both LW and SW UV light.

From Dunning et al., 2019, page 43:

"Calomel is uncommon in the mercury ores. It was found associated with cinnabar, eglestonite and liquid mercury at the McDermitt mine (Rytuba and Glanzman 1979; McCormack 1986), and with photosensitive cinnabar, terlinguaite and an Hg-S-Cl mineral, probably corderoite, at the Opalite mine (McCormack 2000). Recent discoveries of calomel crystals in silica-rich light gray rock associated with kleinite and terlinguacreekite presents an interesting association. Colorless calomel tetragonal crystals up to 0.5 mm cover older quartz in pockets."

The original lithic tuff was reworked fluvially, buried, and then invaded by mercury-bearing fluids and various stages of silica during lithification. Micro-crystalline cinnabar fills pores and fractures in the rock and is covered, in turn, by quartz, powdery colloidal cinnabar, and secondary hypogene Hg minerals like calomel. This means at least some of the cinnabar at this mine is either late-stage or secondary. Eroded tiny HgS crystals are often seen in the samples and support that some of the ore might be secondary, as does the conversion of 25% of the cinnabar orebody to the rather rare alteration product corderoite, Hg3S2Cl2.

Photo taken with D-Lite 5MP USB Digital Microscope.
Copyright: © Michael F. Cox      Photo ID: 983963     Uploaded by: Michael Cox   View Count: 57   Approval status: Public galleries    Type: Photo - 2048 x 1536 pixels (3.1 Mpix)

2ER-JH0Fluorapatite Ca5(PO4)3F , Goethite α-Fe3+O(OH) , Tuffaceous-sedimentary-rock

08110030015655714785201.jpg
McDermitt Mine, Opalite Mining District, Humboldt Co., Nevada, USA

Field of View: 5 mm

Ca-F apatite on vuggy silicified tuffaceous sedimentary rock. Could easily be mistaken for kleinite by a novice. The apatite is more transparent, has relatively indistinct cleavage, does not degrade in sunlight, and is harder (Mohs 5 vs. 3.5). This photo was taken with a cheap USB microscope and is not very good.
Photo ID: 983945     Uploaded by: Michael Cox   View Count: 20   Approval status: Public galleries    Type: Photo - 2048 x 1536 pixels (3.1 Mpix)

219-Y8CGaildunningite Hg2+3[NHg2+2]18(Cl,I,OH,Br,S)24 , Quartz SiO2

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Clear Creek claim, Goat Mountain, New Idria Mining District, San Benito Co., California, USA

Field of View: 0.350 mm

Photograph by Michael F. Cox from a type specimen in the collection of Gail Dunning. Orange gaildunningite on quartz. Identification confirmed per methodology detailed in the "The Canadian Mineralogist," Vol. 57, pp. 295-310 (2019), DOI: 10.3749/canmin.1800080.

Photo taken with Orthoplan compound research microscope fitted with 22x Ultropak system, halogen 100W incident polarized light, Sony A7R full-frame CMOS camera tethered to PC via Remote Camera Control (Copyright 2012-2017 Sony Corporation), 200 stills at 0.5 sec. per still and ASA-50 exposure speed, stacked with Zerene Stacker (Build T2018-07-19-1515, July 19, 2018) and some retouching done with Zerene Stacker to remove dust and eliminate haze.
Copyright: © Michael F. Cox      Photo ID: 958022     Uploaded by: Michael Cox   View Count: 214   Approval status: Public galleries    Type: Photo - 7360 x 4912 pixels (36.2 Mpix)
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