Production History of The Cactus Gold Mine. 7
Cactus Gold Mine Heap Leach Pad. 8
Heap Leach Pad Material Metallurgical Test Using Eco-Goldex O Series. 8
Leaching Results and Discussion. 9
Heap leach Pad Material Estimation. 10
Proposal and Recommendations. 11
Eco-goldex is retained by Ashanti Minerals Group LLC (AMG) of Los Angeles, California, USA, to evaluate the possibility of apply Eco-goldex gold extraction product to recover available gold from a past gold production gold mine heap leach pad, and assess the potential of gold resources at the surrounding areas of the Cactus open pit at Kern county, California.
In June 2017, AMG shipped about 45 lbs materials collected from the historic heap leach pad to Eco-goldex for gold leaching test. Eco-goldex applied its O series reagent to test the materials. After the leaching test, several small pieces of sponge gold were recovered through zinc strip precipitation method in the pregnant solution, and qualitative assay indicates abnormal elevated high gold content in the sample.
With the promising preliminary leaching test result, John Guo (Ph D. P. Geo), the founder and director of Eco-goldex, registered professional geologist in Quebec, Canada, paid a two-day visit at the historic Cactus gold mine leach pad. Accompanied by Mr. Joshua Kwadjo Boateng, the CEO of Ashanti Minerals Group LLC, the author conducted the following tasks during this visit:
Eco-goldex conducted leaching test on the second sample collected by Dr. John Guo and the result has confirmed the first leaching test and at the same time two XRF tests on the second round verification samples still reported abnormally elevated gold grades of 98.0 g/t and 105.0 g/t from two samples collected in the leaching pad.
Based on field investigations and two times leaching test results, the author considers that the Cactus gold mine heap leach pad and its adjacent mine areas are merit for further exploration work and a large scale onsite pilot leaching test is warrant to reveal the economic potential of the historic heap leach pad.
This proposal is prepared based on documents provided by Ashanti Minerals Group LLC and online reports the author searched relevant to the subject topic and leaching test results from samples collected from the leach pad.
The past Cactus gold mine site is located approximately 85 miles northeast of Los Angeles, California, in the Mojave Mining District.
The property is readily accessible year-round by all-weather roads from west off State Highway 14 via the paved Backus Road then north on Tehachapi-Willow Springs Road as shown in the map below and Appendix A. Another currently active mine, the Golden Queen (Soledad gold mine) open pit heap leach operation is about 9 km NE of the site(right side in the image blow) as also shown in the image below.
Figure 1: Accessibility of the past production Cactus Gold Mine site (the left), the active Golden Queen mine is on the right
Gold at the Cactus mine area was first discovered in 1894 on the Yellow Rover vein by George Bowers at Standard Hill, about 3 miles south of Mojave. Underground mining at Soledad Mountain began soon after. Exploration and production in the district quickly expanded, culminating in a discovery at the Cactus Queen (Shumake) vein at Middle Butte in 1934 that substantially boosted district production. Within the district, several other veins were developed, and through 1942 the ores were processed locally.
Gold was mined initially underground at the Cactus Queen Mine from the Cactus Vein from 1934. Total production from the district was $23 million in gold and silver. This early phase of gold mining ended with the War Production Board Limitation Order L-208 of 1942 and subsequent closure of all gold mines in the U.S. (https://mrdata.usgs.gov/mrds/show-mrds.php?dep_id=10310650)
From 1934 to 1962, approximately 92,000 ounces of gold and 2,320,700 ounces of silver were produced (Blaske and others, 1991). In 1986, Cactus Gold Mines Co. began mining initially from the Shumake Pit and later expanded to several satellite pits (Appendix B).
Active open-pit mining ceased in 1992 with leaching of stockpiled ore continuing through October 1996. Total production during this period was about 400,000 ounces of gold and 3,000,000 ounces of silver. Subsequent exploratory drilling in 1997 by Summo Minerals Corp., discovered an additional gold resource beneath the Shumake Pit. The new resource may contain as much as 600,000 additional ounces of gold (Hahn, July 29, 1997 and California geological survey, CGS open file report 99-15). Summo Minerals Corp. elected not to pursue development of the resource, and the property was decommissioned in the late 1996.
Since the beginning of gold production from 1934 to the decommissioning of the mine in 1996, In total, about 500,000 Oz Au was produced, and 5,320,700 Oz Ag were produced(Blaske and others, 1991). Though no ore production statistic number is available prior to 1988, from 1988 to 1992, a total of 4,554,938 Mt ores with gold grade ranging from 0.039 to 0.185 Oz/t were mined and processed at Cactus Gold mine (Blaske and others, 1991). There are still about 600,000 Oz Au in situ resources drilled off under the Shumake pit area by Summo Minerals Corp unexploited (Hahn, July 29, 1997).
Tectonically, this region is part of the San Andreas Fault system (SAFS), which progressively formed when the Farallon-Pacific spreading center collided with the subduction zone (Atwater, 1989). During the Late Cenozoic, this region was first dominated by subduction of plates and then by subsequent movements along the northwest-trending right-lateral SAFS. According to Dokka and Ross (1995), interaction of the Pacific and North American plates during this period of time was directly responsible for regional extension in the western Mojave Desert. The interaction may have been highlighted by transtensional pulling away of the Pacific Plate from the North American Plate (Atwater, 1989) which caused the edge of the North American Plate to extensionally collapse, perhaps by gravitational failure. This extensional activity incurred between 24 and 18 Ma is the mechanic reason that induced the Cenozoic volcanic activity at Soledad Mountain as determined by McCusker (1982). During this tectonic movement, magma may have ascended from the mantle to fill the void between the transform fault system and the broken-off slab that was still descending to the east of the system. The volcanism at Soledad Mountain may have been a local expression of this process.
Various silicic eruptive centers of Tertiary age in this region have been the sites of epithermal precious-metal mineralization. Besides Soledad Mountain, other deposits of a similar epithermal nature within these volcanic centers include Standard Hill, Middle Buttes (Cactus), and Tropico Hill. Extensional environments are favorable for the migration of magmas and associated metal-bearing hydrothermal fluids.
The local geology at Cactus area is composed of a rhyolite to quartz latite flow-dome complex that was intruded into and erupted upon Mesozoic quartz monzonite basement during the early Miocene. It is believed that overlapping with the Miocene volcanism at Middle Buttes were episodes of fracturing and hydrothermal alteration that resulted in gold and silver mineralization.
Gold orebodies are directly constrained in the NE and NW trending normal faults that cut the volcanic dome complex. The NE striking fault system is the most important structure system that controls the Cactus gold mine. These fault system extend several thousand feet along strike.
Gold and silver ores occur within massive and brecciated epithermal quartz veins that follow NW- and NE-trending faults, and intersections thereof. They are also along basement contact zones where advanced alteration developed.
Silicic (early phase, pervasive) Phyllic; sericite (envelopes up to 5m thick surrounding massive quartz veins) Advanced argillic; alunite, kaolinite (peripheral to main ore zones) Potassic; adularia Propylitic; chlorite, pyrite, sericite, calcite (affects basement granitic rocks) are all well developed in the deposit. Nearly all of the rocks at Middle Buttes have been hydrothermally altered. Gold mineralization is associated with advanced argillic alteration and potassic alteration contemporaneous with the Miocene volcanism. The alteration assemblages are zoned with as wide as 5m alteration halos developed.
In the Cactus gold mine, Au-Ag is hosted in quartz-adularia veins and quartz stockwork veinlets within rhyolitic domes and vent breccia at or near the basal contact between the Bobtail Quartz Latite Member and quartz monzonite basement.
Au-Ag ores were initially mined in quartz veins occurring in dacite that strikes NE 45°and dips 35° SE with a width of about 16 ft (Julihn and Horton, 1937). Gold occurs as very fine free gold in quartz vein, along with finely disseminated cerargyrite. The vein lies along a major fault separating Mesozoic quartz monzonite bedrock from Tertiary quartz latite porphyry, and the main ore minerals include proustite, argentite, electrum, and finely divided free gold (Julihn and Horton, 1937). Alteration associated with the quartz veins is a complexly zoned system of lower-most propylitic alteration overlain by silicification and argillic and advanced argillic assemblages of kaolinite, alunite, and sericite (Blaske and others, 1991).
The Shumake ore body contains mercury, arsenic, and antimony (Blaske and others, 1991), which are typical element combination of epithermal mineral deposition at shallow environment as shown in the schematic diagram of epithermal Au-Ag system in the Appendix D.
Soledad Mountain gold mine is an active gold producer currently operated by Golden Queen Mining Company. From 1894 to 1934, this gold mine has yielded approximately $10 million in gold from several quartz veins (Troxel and Morton, 1962). Recent work by the Golden Queen Mining Company, Ltd. has defined a drill-indicated resource totaling 86.5 million metric tonnes of ores with an average grade of 1.0 gram of gold per tonne (1 gram per tonne equals 0.0292 ounces per ton) and 14.4 grams per tonne silver. The deposit contains an estimated 2.43 million ounces of gold and 39.6 million ounces of silver making it the largest precious metal resource known in Kern County (Banning, 1998).
Gold mining Workings at the Cactus gold mine include surface and underground openings. Before 1980s, gold and silver mining at Cactus (also called Middle Buttes) was through standard underground workings (shafts, adits, drifts, and crosscuts), which cumulatively amounted to many thousand feet at several mines. Begun in late 1980s to early 1990s, ore bodies at Middle Buttes were exploited through open-pit, heap-leach mining techniques. Both Merrill–Crowe Process and activated carbon absorption process were used to precipitate gold from pregnant solution during the 1980-1990’s operations.
In the late 1980s and early 1990s, the mining operations consisted of one large open pit (Shumake) and several smaller ones (Silver Prince, Winkler, Alunite, Ella, and Trent). The Shumake Pit reached a depth of 640 feet below the ground surface. It eventually merged with the Silver Prince Pit to form a single pit about 1,300 feet wide and 2,500 feet long.
Production statistics data at Cactus gold mine is not complete and different sources reported different numbers. According to USGS, Troxel and Morton (1962) reported the value of total production from the Cactus Queen Mine at more than $5 million (gold + silver). Blaske and others (1991) reported that the Cactus Queen produced 92,000 Oz Au and 2,320,700 Oz Ag between 1934 and 1962, and production of gold at the modern Cactus Gold Mine operations from 1986 to 1996 is estimated to be less than 500,000 Oz.
The table below lists Production statistics from the year of 1989 to 1995 compiled from Hecla Mining company historic report, gold ores mined were about 4,554,938 tons with average gold grades ranging 0.03 – 0.06 Oz/t, and full production costs range 309-437 USD/Oz in these years:
Operation Year | Au(Oz) | Ag | Ores(Mt) |
1989 | 59,493 | 266,643 | 2,106,800 |
1991 | 53,912 | 217,014 | 2,129,724 |
1992 | 36,283 | 138,394 | 318,414 |
1993 | 9,755 | 32,220 | 0 |
1994 | 10,147 | 26,074 | 0 |
1995 | 5,295 | 2,324 | 0 |
total | 174,885 | 682,669 | 4,554,938 |
A heap leach pad with open pit method was formed on the property from 1989 to 1994 and ended circa 1996.
The past Cactus gold mine heap leach operation photo is shown in the Appendix E-1 and the current pad shape is shown in the E-2.
Ashanti Minerals Group LLC has identified the Cactus Gold mine heap leach pad to evaluate the possible reprocess operations to extract precious metals in the pad, and Ashanti Minerals Group recently inked an initial agreement with the private owner of the SW end portion of the pad, to develop this project. In this agreement, the owner and Ashanti Minerals Group LLC. will take 50-50% interest on the project. The land owner will be responsible for to bring in all onsite infrastructure including the ownership of the pad to the JV, AMG is responsible for financing and technical operations of the project. AMG also intends to expand reprocessing of the whole pad should the first section pad reprocess project be successful.
AMG collected and shipped about 45 lbs heap leach tailing materials collected at the Cactus property to Eco-goldex for leachability test of gold in the pad. Eco-goldex conducted a miniature VAT leaching test on the materials received. Below are the leaching test parameters used:
Leaching pregnant solution is treated with zinc strips to precipitate gold out of the preg-solution. About 55 grams of zinc strips were used to precipitate gold in the preg solution. After series chemical process, several small pieces of sponge gold were recovered as shown in Appendix F. This test is very exciting and promising, at the same time, eco-goldex assayed the materials received and noticed abnormal elevated gold grade of 25 g/t Au in the sample.
In the second round samples the author collected during site visit, XRF assay result verified the same abnormal elevated gold grades in the samples. The table below shows the assay results of the second round sample assaying:
CaO(%) | S(ppm) | Sb(ppm) | As(ppm) | Au(g/t) | |
Red color sample | 0.21 | 670 | 115 | 5760 | 98 |
Orange color sample | 0.22 | 1670 | 164 | 6637 | 105 |
Eco-goldex has discussed with Ashanti Minerals Group about the possible factors that caused the abnormal elevated gold grades in the samples. Following information and facts that may attribute to the elevated gold grades phenomena:
Eco-goldex is an eco-friendly reagent invented and produced with the goal to replace the toxic sodium cyanide in gold extraction process. Eco-goldex owns this technology and its clients are from 45 countries. Eco-goldex O series is only about 1% in the toxicity compared with cyanide. Eco-goldex O series is categorized as ordinary product can be transported by all transportation means(air cargo, train, vehicle, marine vessel..) and stored in normal conditions without any special permit requirement.
Based on the information provided by AMG and field discussion with the land owner, the author defined the scope of the portion that AMG has the permission to work on with the private owner. The heap leach pad geometry is depicted as shown in Appendix H.
Please note that all the measurements are based on google earth, the elevations and perimeters measurement may not be as accurate as they should be. The material volume and material tonnage have their preliminary nature; these measurements will be revised in the field with more accurate measurement methods and tools in next step. The estimated volume and material tonnages are provided for reference only.
The SW ending pad portion in this subject can be depicted as a trapezoidal form shown below. All the measurements are based on google earth 2016 image information. Based on these measurements, the volume of the trapezoid is about 604,000 M3, assume rock density is 2.2 t/M3, then the material tonnage AMG has access can be rounded about to 1,330,000 tons.
Not applicable at this stage
Based on the preliminary leaching test results, assay results, field investigation, and historic drilling results, Eco-goldex considers that the SW portion of the past heap leach pad has demonstrated good promising gold leachability and abnormal elevated gold grades that warrant for further investigation and economic evaluation through a large scale onsite pilot leaching test, the nearby area under the Shumake gold mine pit, especially the portion between100-200m depth, warrant to further drilling exploration program. The following tasks are recommended to Ashanti Minerals Group LLC.
The table below lists the estimated budget to conduct the proposed tasks.
Series | Tasks | Estimated budget | Goals |
1 | 5-10 tons large scale onsite pilot leaching test at the heap pad | 55000 | To assess gold leachability and production rate of the heap leach pad |
2 | Sampling at heap leach pad (50-100 samples) | 5500 | To collect material gold grades in the SW end portion pad that to be reprocessed, this data set will be used to calculate gold resource available in the pad |
3 | 8000m drilling program | 1,600,000 | Drill exploration around the Shumake pit and its surrounding areas. Including |
4 | Drilling program implementation cost (project planning, execution, management, data compilation and processing, resource modelling) | 255,000 | Hiring technical staffs or consultants to plan, execution exploration program, data compilation, interpretation, resource modeling. |
5 | Sample assay cost (~2200 samples) | 100,000 | 1/3 of the drilling meters will be sampled and assayed for resource estimation purpose |
6 | NI43-101 report | 50,000 | Technical Report comply with the NI43-101 regulation |
7 | Contingency | 310,000 | About 10-15% |
8 | Total | 2,400,000 | Total budget proposed for the whole program |
Location of the historic Cactus Gold Mine property
Schematic diagram of epithermal Au-Ag system, the current Au-Ag mineralization depth controlled and the significant target should be explored by drilling in the next step.
The Heap leach pad of the Cactus gold mine at different time period.
E-2
Pieces of sponge gold recovered from the first 45 pounds of tailing materials leaching with eco-goldex O series
Indicative movement of pregnant solution inside leach pad (blue arrow) and the heap leach pad construction direction (with red arrow and chronological sequence) in the Cactus gold mine.
Blaske, A.R. and others, 1991, The Shumake volcanic dome-hosted epithermal precious metal deposit, western Mojave Desert, California: Economic Geology, v. 86, p. 1646-1656.
Hahn, GA., July 29, 1997, Cactus Gold Mines, continued drilling extends Shumake Orebody: Toronto Stock Exchange, Summo Minerals Corp. Press Release #97 -21 , http://www.summominerals.com/press/ jul7 -97.html (broken link), 2 p.
Atwater, T., 1989, Plate tectonic history of the northeast Pacific and western North America, in Winterer, E.L. and others, editors, The eastern Pacfic Ocean and Hawaii: Geological Society of America, The Geology of North America, v. N, p. 21-72.
Dokka, R.K. and Ross, T.M., 1995, Collapse of southwestern North America and the evolution of early Miocene detachment faults, metamorphic core complexes, the Sierra Nevada orocline, and the San Andreas fault system: Geology, v. 23, no. 12, p. 1075-1078.
McCusker, R.T., 1982, Geology of the Soledad Mountain volcanic complex, Mojave Desert, California: San Jose State University, M.S. thesis, 113 p.
Julihn, C.E. and Horton, F.W., 1937, The Golden Queen and other mines of the Mojave District, California: U.S. Bureau of Mines Information Circular 6931, 42 p.
Troxel, B.W. and Morton, P.K., 1962, Mines and mineral resources of Kern County, California: California Division of Mines and Geology County Report 1, 370 p.
Banning, S. W., October 2, 1998, Golden Queen increases ore reserve gold by 16%: Golden Queen Mining Co., Ltd. news release, http://www.goldenqueen.comlnewsI981002.htm. 2 p.