ICP Analyses from the Cinnabar-Mercury Occurrence at Azogues ( Loma Guashon ) , Ecuador : Ancient Industrial Uses and Human Health Implications

ICP (Inductively Coupled Plasma) analyses of the Cretaceous marine sandstones at the Azogues (Loma Guashon), Ecuador cinnabar-mercury occurrence gave 11 113 ppm Hg. However, the ancient Azogues mines have been well documented previously, for example: 1) a 1799 hand drawn map “Plan del Cerro Mineral de Azogue” shows numerous adits; 2) during Colonial time, Cuenca founder, Gil Ramirez Davalos was owner of the mercury mines; 3) in the late 1800s, Teodoro Wolf described well-worked adits at Guashon and samples with 0.5% Hg; and more recently, 4) the Metallogenic Map of Ecuador shows the mercury occurrence at Azogues. Mineral resource assessment of the Azogues occurrence is important to regional archaeological studies of resource availability and ancient use of cinnabar as a pigment and as a source of mercury for gold amalgamation before the arrival of the Europeans, and possibly later, for silver amalgamation, during Colonial time.


Introduction
Mercury and cinnabar occurrences are known throughout the Andes and blood-red cinnabar (HgS), the ore of mercury, was mined, selectively sorted, and ground for use as a pigment (vermilion), in funeral rituals, and as makeup during pre-contact time (Whitaker, 1941;Petersen, 1970Petersen, /2010;;Brown, 2001;Brooks et al., 2008).

Previous Work
The cinnabar-mercury occurrence at Azogues, also referred to as Loma Guashon or Huashun, is approximately 4.5 km east of the town of Azogues (Azogues, 1968).And, even though several geologic references are readily available, the Azogues cinnabar occurrence was dismissed, without field study or thorough review of the literature, as a "red herring" in Andean mineral resource studies by Berger et al. (2016).

Previous work includes:
• A sketch map "Plan del Cerro Mineral de Azogue nombrado Guazun (Guashon)" that dates to 1799 shows the adits oriented along the north-south strike of the cinnabar vein (Archivo General de Indias, 1799) (Figure 1; Figure 2).Whether these mine workings date to Colonial time, or earlier with possible Colonial overprinting, has important implications for regional archaeological and mineral resource studies.Herein, these adits are interpreted to have initially been worked before the arrival of the Europeans.The evidence includes: 1) the numerous adits are shallow and follow the easy-access surface exposures of the cinnabar ore, and similarly, Petersen (1970Petersen ( /2010) ) indicates that pre-contact underground mining, such as interpreted at Azogues, seldom went for any depth and was typically limited by how far the sunlight could reach into the adit.The absence of mine waste near the entrance also indicates shallow workings.Early mines in Europe rarely penetrated more than 10 m (Craddock, 1995) and the Azogues adits, in comparison, may only reach ~15 m (Table 1).Also see Figure 1 and note the presence of llumbreras (described in legend at lower left) that have been interpreted as smaller adits cut to the surface to serve as a light source; 2) there are no remnants of interior beams or supports; 3) pre-contact mining was typically limited to softer rocks such as the sandstones and shales (Figure 3) found at Azogues (Egüez, 1993a;1993b); 4) ancient mines typically followed the veins and ore pockets, and not a compass direction, and therefore, were likely to be sinuous (Craddock, 1995); 5) the floors of ancient mines were seldom horizontal; and 6) the Azogues adits do not have the stone entrance     Cerro Azogue (Guashon); however, no data on mine production was included.Therefore, Azogues may have been a Colonial source of mercury, however, Azogues was a far smaller occurrence and less important than Huancavelica's mercury that was used for silver amalgamation during the late 1500s.
• Wolf (1892Wolf ( /1975) ) (Egüez, 1993a) shows Cretaceous sandstones and other sedimentary rocks at Azogues and, most importantly, the companion Metallogenic Map of Ecuador (Egüez, 1993b) shows a mine symbol with the number 117 that corresponds to "Hg" in the accompanying list of Names and Details of Metallic Mines included on the map explanation.Delbridge & Robertson (1992) also indicate that Azogues is the only mercury occurrence in Ecuador; however, two other occurrences, Cerro de Camachurco and San Jacinto, are referenced by Chacon (1986) and Vetter Parodi (2016).Other mercury occurrences spatially associated with Ecuador's epithermal porphyry gold-copper systems (Gemuts, 1992;Howell International, 2014)

ICP Data from Azogues
As noted by Wolf (1892Wolf ( /1975) the Azogues mines had been exhausted of their native mercury; however, rock samples sent to Lima contained 5000 ppm Hg.
Therefore, mercury occurrences such as Azogues should be evaluated using modern geochemical methods to document the ore that was produced.
Using the basic tools of mineral resource assessment that include a site visit and geochemical sampling (Inductively Coupled Plasma), the altered sandstones in the adits at Azogues gave 11.8 -113.3 ppm Hg (Table 1), which is consistent with mining that would have long since removed the high-grade cinnabar ore and native mercury leaving only trace amounts of disseminated cinnabar (Duschak & Schuette, 1925) in the wallrock along the north-south structure (Figure 3).Craddock (1995) also indicates that Bronze Age miners in Europe were similarly thorough "…and removed every last morsel of ore before a working was abandoned." Occurrence of the mercury in association with the sedimentary rocks at Azogues is somewhat similar to the geologic setting of Almadén, Spain where the ore is also stratabound, disseminated cinnabar with some native mercury.The geochemical signature at Azogues is much like the geochemical signature at Almadén and Huancavelica (Rytuba, 1986;Noble & Vidal, 1990) and includes As (9 -75 ppm), Sb (10 -54 ppm), and other elements of interest such as Ag (0.3 -2.4 ppm) and Pb (12 -220 ppm).Background elemental concentration for sandstones is also provided on Table 1.The amount of sulfur (182 -7262 ppm) may be related to the sulfur held in cinnabar; however, other sulfur-bearing minerals may be present.Altered rhyolite was found at one location (

History of Retorting and Ancient Industrial Uses
Retorting cinnabar to obtain mercury dates to 8,000 years ago in ancient Turkey where the 3 m marble base of an ancient retort was found.The metal would have been used for gilding and alluvial gold amalgamation (Barnes & Bailey, 1972;Brooks et al. 2017).Fine-grained gold from the Takht-e Soleyman mining district, northwest Iran, was first panned and then mixed with mercury for retorting (Momenzadeh et al., 2016).And, also in Mesopotamia, ancient cinnabar processing on a smaller scale is indicated by the Tepe Gawra pot (3500 BC) that has been interpreted as an ancient mercury retort (Levey, 1955).
The earliest written description of mercury used for alluvial gold mining was by al-Biruni, an 11 th century Persian scientist.Small pits in the Sind (Indus) Riverbed were filled with mercury; the mercury amalgamated the alluvial gold flakes and then the mercury-gold amalgam was recovered, squeezed in a cloth to remove most of the mercury, and then the amalgam "nugget" was burned to volatilize any remaining mercury (al-Hassan & Hill, 1986).This anthropogenic gold "nugget" could then be fashioned into jewelry or hammered to produce gold foil.
In Europe, Agricola (1556Agricola ( /1912) ) indicates that the use of mercury for gold amalgamation dates at least to Roman times, whereas the use of mercury for silver amalgamation dates only to the 16 th century.This chronology is consistent with the onset of the use of mercury from Huancavelica, Perú and mercury imported from Almadén, Spain for silver amalgamation, specifically the Patio Process, during Colonial time in the New World (Barba, 1640(Barba, /1923;;Crozier, 1993;Robins, 2011).
In Perú, ancient retorting is indicated by ceramic retorts (hornos antiguos) that date to AD1400 that were found near the Huancavelica mines (Rivero & Tschudi, 1851in Petersen, 1970/2010).Therefore, retorting cinnabar and the end-uses of the mercury in the ancient Andes, whether from Huancavelica, Azogues, or any of a number of other mercury occurrences, are thoughtprovoking.And, given the availability of cinnabar and the amount of gold masks, pectorals, and other gold artifacts that were produced before the arrival of the Europeans, then retorting of cinnabar and amalgamation are consistent with any discussion of ancient gold mining and artifact production in the Andes.
The mercury produced from the ancient Huancavelica retorts would have had but one use-much as mercury is widely used today-for small-scale alluvial gold mining (Cabrera La Rosa, 1954;Larco Hoyle, 2001;Sandoval, 2001;Cánepa, 2005;Brooks et al. 2013).

Human Health
In Perú, Garcilaso de la Vega (1539-1616) commented that mercury fumes were W. E. Brooks DOI: 10.4236/ad.2018.6100346 Archaeological Discovery unhealthy and inhalation resulted in "shakes" and loss of other senses (Brown, 2001;Larco Hoyle, 2001)-this observation regarding mercury and human health is very important.The implications are straightforward and provide evidence of 3 possible ways in which the ancient Andean miners and metallurgists would have been exposed to mercury fumes: 1) during ancient cinnabar mining and fire setting-Similar to Garcilaso de la Vega's observations in Perú, modern cinnabar mining at Almadén exposed workers to mercury dust and fumes that affected the nervous system (Putman, 1972).However, because of the smoke, dust, fire, heat, toxic fumes, and sulfurous smell resulting from the ancient method of fire setting, the mine would have been evacuated (Craddock, 1995).The cinnabar recovered from this process would have had two industrial uses: 1) sorted and ground for use as a pigment, or 2) retorted to provide mercury.
2) during ancient cinnabar retorting- Agricola (1556Agricola ( /1912) ) showed racks of ceramic retorts being fired and also warned of the adverse health effects of breathing the sweet-smelling mercury fumes that were released during retorting.
When cinnabar is retorted, the metallic bonds between mercury and sulfur are irreversibly broken and do not recombine to precipitate as cinnabar.Therefore, in the retort in the presence of oxygen, the products would have been sulfur dioxide (gas) and mercury vapor that would have been cooled, condensed, and collected as liquid mercury (Roskill, 1990), as in the following reaction: HgS + O 2 = SO 2 + Hg (Duschak & Schuette, 1925).
However, owing to the imperfections in the ancient ceramics or in the seals between the ceramic vessels, then this process would have released Hg fumes, along with SO 2 , from the retorts or up the chimney (Brooks et al. 2017).Any of the pink-to light-red calcined material resulting from retorting may have been plowed under, covered by jungle growth, debris flows, or removed by rainfall.
Retorting would have provided mercury to be used for ancient small-scale alluvial gold mining.
3) or from burning (refogado) the gold-mercury amalgam-in order to part the alluvial gold from the mercury-gold amalgam "nugget", the "nugget" was burned (refogado) with a blowpipe (soplete), or in modern times, with a gas torch.This burn would have released dark mercury fumes that modern miners and gold dealers in Madre de Dios or southern coastal Perú, for example, rigidly avoid during amalgam burning (Cánepa, 2005).A Benzoni sketch from the 1500s (Petersen, 1970(Petersen, /2010) ) shows that their "sopletes" are above the flames.
This would have concentrated and provided higher oxygen content, which in turn provided the higher temperatures necessary to volatilize the remaining mercury and melt the gold (1063˚C), much as an analytical blowpipe was used for mineral analysis in the 1700 -1800s.This analytical technique, which dates to 1500 BC and was used by Egyptian goldsmiths, was widely used for analytical chemistry of minerals through the mid-1800s (Dana & Ford, 1922;Jensen, 1986).
The Benzoni sketch shows how the workers would have been exposed to the  (Roskill, 1990;Cánepa, 2005) would have been released, as toxic fumes, during the refogado process (Brooks et al., 2007;2013).
Fuel for retorting would have been supplied from the abundant eucalyptus trees in the region or possibly from lignite in the Cuenca-Azogues-Biblian region (O'Rourke, 1978;Weaver & Wood, 1994;Hackley & Brooks, 2006).

Conclusion
Cinnabar and mercury were known and used for only two purposes in the pre-Columbian Andes and mercury was essential to Colonial silver processing.
Therefore, site visits, geochemical sampling, and assessment of the cinnabar occurrences in the Andean region, such as Azogues, are important to understand the availability of cinnabar and mercury for ancient industrial applications that included: 1) pigment production, and 2) retorting cinnabar to obtain mercury for small-scale gold production.Geochemical sampling, combined with information from published documents, unequivocally indicated the availability of cinnabar and mercury at Azogues (Loma Guashon).The number of shallow workings and geometry of the Azogues adits combined with the lack of stone entrance architecture and other physical evidence at Azogues are consistent with initial pre-contact cinnabar mining for ancient industrial uses such as vermilion production and mercury retorting.However, the absence of Colonial entrance architecture indicates that it was unlikely that the Azogues occurrence was a significant source of Colonial cinnabar.

Figure 1 .
Figure 1.A sketch map of "Cerro Mineral de Azogue nombrado Guazun (Guashon)" that dates to 1799 showing adits oriented along the north-south strike of the cinnabar vein (Archivo General de Indias, 1799).

Figure 2 .
Figure 2. Lowest adit shown in Figure 1, note the absence of any entrance architecture.

Figure 3 .
Figure 3. Sheared, altered sandstone at entrance to adit shown in Figure 2.
architecture typical of mines that were exploited mainly during Colonial time, for example, the Santa Barbara mercury mine, Huancavelica, Perú (Figure 4(a), Figure 4(b)), or the La Candelaria silver mine, Potosí, Bolivia (Figure 4(c)).• Chacon (1986) discussed Gil Ramirez Davalos' (governor of Quito and founder of Cuenca in 1557) Colonial ownership of the mercury mines at Figure 4. (a) Colonial stone architecture (interior and right of archway) at entrance to Santa Barbara mercury mine, Huancavelica, Perú; (b) Carved Spanish shield at entrance to Santa Barbara mercury mine, Huancavelica, Perú; (c) Colonial stone architecture, with modern mining equipment, at entrance to La Candelaria silver mine, Potosí, Bolivia (http://www.loupiote.com/photos/5043777416.shtml).
may have been overprinted or removed by recent mining.• Truhan et al. (2005) researched "…the site of the Colonial, and possibly pre-Columbian, Azogues mines that were found near the municipality of Luis Cordero at Loma Huashún and ancient mining evidence included reddened scoria." visited the Azogues area and documented "…old mercury mines in the Huaizhun (Guashon)… with large well-worked galleries… but not a drop of native mercury was found… it appeared that the occurrence " and he suggested that the mercury was released during small-scale gold mining (pre-contact?orColonial?) by lavaderos (small-scale gold miners) panning in the region.•The Geologic Map of Ecuador loupiote.com/photos/5043777416.shtml).was completely exhausted... however; rock samples sent to Lima gave ½% Hg (or ~5000 ppm Hg)."He also reported that campesinos (farm workers) near the mines found azogue in the soils and "…mercury droplets were found at Peñas de Guayaquil… at the foot of Cerro Santa Ana… in the Rio Guayas… W. E. Brooks DOI: 10.4236/ad.2018.6100344 Archaeological Discovery and Rio Daule