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Otis commences 2019 step out drill program at Kilgore Project (see news release dated Oct. 2, 2019)


The Kilgore Project consists of 614 federal lode mining claims totaling 12,150 acres (49.2 km2) located on US Forest Service land in southeastern Idaho within Clark County, 60 miles north of Idaho Falls. The project is accessible by road approximately 32 miles northeast of the town of Dubois and Interstate Highway 15.

The Kilgore Project lies on the north-eastern margin of the Miocene-Pliocene Kilgore Caldera complex in the Eastern Snake River Plain, Idaho. The Kilgore Project contains the Kilgore Deposit with a current NI 43-101 (completed in 2018) Indicated Resource of 825,000 ounces (oz.) Au in 44.6 million tonnes at a grade of 0.58 g/t Au and an Inferred Resource of 136,000 oz. Au in 9.4 million tonnes at a grade of 0.45 g/t Au (the “Deposit”). The Kilgore Deposit is a low-sulphidation, gold bearing, quartz-adularia epithermal system hosted in Tertiary volcanic rocks, local Tertiary intrusive rocks, and basement Late Cretaceous, Aspen Formation sedimentary rocks. The release of an updated NI 43-101 compliant resource calculation was announced on Aug. 14, 2018 (please see Otis news release dated Aug. 14, 2018) and the technical report has been filed on sedar.

2018 Kilgore Project NI 43-101 Technical Report and Mineral Resource Estimate dated August 14, 2018



Resource Category
Tonnes (MM)
Grade Au (gpt)
Contained Ounces Au


Kilgore Deposit – Indicated Resource Model Kilgore Deposit – Au Grade Block Model Kilgore Deposit – Au Grade Block Model looking South

Otis Amends and Files maiden Preliminary Economic Assessment (PEA) (please see Otis news release dated Aug. 27, 2019)

Independent Technical Report and Preliminary Economic Assessment, Kilgore Project, Clark County, Idaho, USA – August 2019

PEA Highlights

  • After-tax NPV (5% discount rate) of US$110.4 million and IRR of 34.0 %, with a 3.0-year payback period and LOM net cash flow of US$151.8 million;
  • Pre-tax NPV (5 % discount rate) of US$144.0 million and IRR of 40.6%;
  • Total amount of gold recovered is estimated at 558,700 ounces;
  • Average annual gold production of approximately 111,700 ounces;
  • Peak annual gold production of approximately 119,600 ounces in year 1;
  • Mine life of 5.0 years with a 1-year preproduction period;
  • Average crushed material gold grade of 0.72 g/T (grams per Tonne) and average ROM gold grade of 0.24 g/T;
  • Low LOM strip ratio of 1.1:1;
  • Royalties – 0%;
  • LOM direct operating cash cost1 is estimated at US$780/oz of gold recovered and average LOM all-in sustaining cost (or “AISC”2) is estimated at US$832/oz of gold recovered;
  • Pre-production initial capital cost estimated at $US81.23 million, using contract mining; and
  • LOM capital costs estimated at US$97.5 million.  

1Cash cost includes mining cost, mine-level general and administrative, leaching, and refining cost.
2 All-in sustaining cost (AISC) includes cash cost per ounce, sustaining capital and closure costs.


Otis Gold Corp. maintains a 100% ownership interest in the Kilgore Project. The project is not subject to any royalties, back-in rights, payments or other agreements and encumbrances. No environmental liabilities are currently known to exist.

Property Background

Major gold mining companies spent more than $8 million for property acquisition, drilling 197 holes totaling 38,500 metres, geophysical and geochemical surveying and metallurgical testing on the project from 1983 to 1998. The last exploration conducted on the property by a major company was 1996. Late in the season of that year, a major geochemical soil anomaly was identified and an extensive airborne geophysical survey was completed in the fall of 1996. The survey identified a number of strong anomalies which are coincident with the large geochemical soil anomaly.

In the fall of 2003, Kilgore Minerals carried out a program of geologic mapping, surface sampling and structural interpretation on the property. This field work resulted in the development of a more comprehensive understanding of the structural fabric and controls of the gold mineralization on a property-wide scale than were previously understood. As a result, a number of highly attractive new targets for drill testing were developed.

In 2004, Kilgore Minerals carried out a diamond drill program of six holes totaling 1,621 metres. The drill program discovered a 10-foot high-grade gold section of 14.5 g/t Au within a 170-foot zone of low-grade gold mineralization (1.25 g/t Au). Subsequently, Kilgore Minerals (which also controlled a range of uranium assets in the USA) was acquired by Bayswater Uranium Corp. ("Bayswater"). Otis acquired the property from Bayswater in 2008.


The project is a volcanic hosted epithermal gold deposit related to a zoned epithermal hot-spring system in volcanic rocks of Miocene age. Gold mineralization appears to be localized by west-, northwest-, and northeast-trending structure. The deposit is hosted within sericitized, silicified and quartz-stockwork veined lithic tuff, dike and silicified clastic sedimentary rocks.

Exploration Summary

Otis has been active on the property continuously since 2008. As part of its 2008 work program, Otis permitted 20 drill sites under Plan of Operations with the US Forest Service and completed 4 core holes totaling 635 metres (m) at the Mine Ridge. All of the drill holes were found to be mineralized. In 2009, the Company completed 12 core holes totaling 3,100 m at Mine Ridge and conducted an 8.5 line km CSAMT geophysical survey at Dog Bone Ridge.

Otis's 2010 Work Program, consisted of approximately 6,300 m of drilling using two drill rigs to test and expand the Kilgore Deposit in the Mine Ridge area. The Company also completed an Environmental Scoping Study, which indicated there are no impediments to permitting an open-pit heap leach operation.

In 2011, Otis drilled 9,320 m at the Kilgore Deposit area. Highlights include intercepts of 114.3 m @ 0.89 grams per tonne gold (g/t Au), that includes 80.8 m @ 1.10 g/t Au in hole 11 OKC-258, 118.8 m @ 0.89 g/t Au, that includes 36.5 m @ 1.65 g/t Au in hole 11 OKC-259, 48.8 m of 1.05 g/t Au, along with an additional 15.2 m of 1.39 g/t Au in hole 11 OKC-265, located on the southern margin of the deposit, and additional intercepts of 39.6 m of 0.70 g/t Au in hole 11 OKC-281 and 30.5 m of 0.68 g/t Au in hole 11 OKC-280, both located in the deposit’s newly discovered, open-ended northwest extension where ore-grade intercepts in excess of 100-m thick were discovered.

As well, in 2011 Otis announced the results of 681 soil samples collected from two grids (the "North Soil Grid" and the "South Soil Grid") situated along the strike projection of the Northwest Fault, known to be the feeder to the Kilgore Deposit. Sampling of the North Soil Grid was performed in order to extend the strike length of the Mine Ridge Deposit northward of the +100 metre thick intercepts that were recently discovered on the northern edge of the 2011 drill pattern (see news releases dated November 1, 2011 and October 6, 2011). The results from the North Soil Grid display strong linear gold-in-soil anomalies that trace the extension of the Northwest Fault for a minimum of 400 metres to the northwest and represent the surface manifestation of feeder faults that supplied the gold-rich hydrothermal fluids into the deposit’s host rocks.

Sampling of the South Soil Grid was performed in order to better define drill targets in the Prospect Ridge target area, located immediately to the southeast of the Mine Ridge deposit. Results from the South Soil Grid identify a large and previously untested, anomalous area in the Prospect Ridge target area.

The North Soil Grid comprises 266 samples collected on a 30-metre x 30-metre spacing in an untested area northwestward beyond the northern limit of the current Mine Ridge Deposit. The data collected and contoured display a strong and significant linear gold-in-soil anomaly that very closely lines up with the trace of the Northwest Feeder Fault that controls the overall northwest trend of the deposit. The anomaly extends the target a minimum of 400 metres in the northwest direction and is shown on the following map http://www.otisgold.com/_resources/kilgore/20120131_Soil_Survey_Results.pdf. These trends, as well as several additional linear anomalies, are collectively considered to be high-priority drill targets that could extend and expand the existing deposit by more than 30%. There are also a number of corresponding trace element anomalies that have a high correlation to the gold suggesting geochemistry characteristics of a typical epithermal gold system.

The South Soil Grid comprises 415 samples collected on a 30-metre x 60-metre grid that displays a very strong and coherent gold-in-soil anomaly that covers approximately 15,000 sq. metres in the Prospect Ridge target area. This anomaly overlies a section of lithic tuff that is identical to rock that hosts the bulk of the Mine Ridge deposit. This portion of the property package has not been drill tested.

Highlights of the 2012 fall drill program includes intercepts of 82.3 m of 0.95 g/t Au in hole 12 OKR-291, 121.9 m of 1.04 g/t Au, that includes 45.7 m of 1.52 g/t Au, in hole 12 OKR-292, and 83.8 m of 1.12 g/t Au, that includes 30.5 m of 2.10 g/t Au, in hole 12 OKR-294.  The program consisted of 1,009 metres (3,310 feet) of drilling in 6 reverse circulation (“RC”) holes designed to offset and extend the 100-metre-plus thick, near-surface intercepts encountered in Otis discovery core holes drilled into the North Target area in 2011 (see Otis October 6, 2011 News Release).

After a 2 year pause, Otis resumed drilling in 2015 with a fall drill program where bulk-tonnage intercepts ranging from 50 to 100 m thickness and grading from 0.57 to 4.24 g/t Au have been intersected. Noteworthy intercepts of significant thickness and grade include: 56.4 m of 2.05 g/t Au in hole 15 OKR-304 (ended in mineralization), 59.5 m of 3.79 g/t Au in hole 15 OKR-305, 50.3 m of 4.24 g/t Au in hole 15 OKR-308 (ended in mineralization) and 94.5 m of 4.21 g/t Au in hole 15 OKR-309 (ended in mineralization).

On July 25, 2016, announced it commenced a first phase 5,500m, 20 hole drill program with a second phase program planned to follow shortly thereafter.  The first six holes of this drill program returned bulk-tonnage intercepts ranging from 55m to 120m thick, grading 0.82 to 1.55 g/t Au. Due to the ongoing success of this program and availability of capital, the drill program was expanded to approximately 9,000 m over 36 holes. Noteworthy intercepts from the first six holes include: 56.4 m of 0.85 g/t Au in hole 16 OKR-316 (bottomed in Aspen Formation), 61.0 m of 1.03 g/t Au in hole 16 OKR–317 (largely in Aspen Formation), 120.4 m of 1.55 g/t Au in hole 16 OKR-318 (hosted in Tertiary sill and Aspen Formation) and 55.5 m of 0.82 g/t Au in hole 16 OKR-321 (hosted in lithic tuff and Tertiary sill).

Further intercepts from this drill program returned 30.5 m of 5.37 g/t Au in hole 16 OKR-315 and 114.3m of 1.00 g/t Au in hole 16 OKR-327.  The 2016 drill program was once more expanded to now 10,300 m in over 40 holes. Further hightlights of intercepts include, 85.4 m of 2.50 g/t Au in hole 16 OKR-338, 69.1 m of 2.07 g/t Au in hole 16 OKR-348 and 50.3 m of 2.04 g/t in hole 16 OKR-330

Highlights from the 2016 drill program and of importance to the future development of the Kilgore Deposit include:

  1. Twenty-five of the 40 holes drilled in 2016 encountered mineralization in the newly-emerging Aspen Formation host. 
  2. An additional 11 holes encountered mineralization in Tertiary lithic tuff and dikes, the primary host of gold mineralization within the existing deposit. 
  3. In total, 36 of the 40 holes drilled in 2016 intersected reportable gold mineralization, representing a drill success rate of 90%.
  4. A complete Table of 2016 drill results can be found on the Otis website.
  5. Results of Otis’ 2016 drill campaign continue to support the premise that gold mineralization in the Aspen Formation is more extensive than indicated by previous drill testing and appears to lie along a northwesterly-trending belt or corridor in the northern half of the deposit, much of which remains open for further drilling.
  6. Results of drill holes targeting the basement Aspen Formation sedimentary host rocks continue to reveal the presence of significant open-ended mineralization that is typically higher-grade and displays thicker mineralized intercepts than those comprising the current bulk of the deposit in the overlying volcanic host rocks.
  7. Reported intercepts in basement Aspen Formation sedimentary rocks demonstrate that mineralization exists to depths of up to 300-meters below the surface of the deposit, with some still open at depth.
  8. The Tertiary intrusive sill (Tct), which directly overlies the Aspen Formation and locally intrudes the upper portion of it, has been proven to host significant mineralization and the extensive contact between the two rock types is an important locus for additional mineralization in the basement. Significant intercepts can and do exist in both the Aspen Formation and the Tct, and in many cases straddle the contact between them to occur continuously throughout both units.
  9. Some intercepts drilled in Aspen Formation rocks along the mineralized northwest-trending corridor contain coarse-grained visible gold indicative of potential bonanza grades at depth.

In 2017, Otis completed 24 exploration holes in 8,000 metres of drilling (see link to complete table of the 2017 drill results). The 25th hole drilled in the 2017 work program was a PQ-sized core hole designed for metallurgical testing purposes. Results of column leach and other testing on this hole can be viewed in the metallurgy tab.

The Qualified Person under National Instrument (NI 43-101) Standards of Disclosure for the technical information on the Otis Gold Corp. website is Alan Roberts (CPG), Vice President of Exploration, who has reviewed and approved its technical content.


Metallurgical testing of the Kilgore Deposit has been ongoing since the 1990’s; the following represents a summary of the metallurgical test results to date. It is important to note that tests conducted before the introduction of NI 43-101 do not meet reporting requirements and are provided for reference only.

Metallurgical Testing Results - 2019

In December 2019, results were received for metallurgical testing from an additional 450 kg of PQ core from drill hole 17OKC-379 from Resource Development Inc. (RDi) of Denver, Colorado under the supervision of Global Resource Engineering Limited (GRE) of Denver, Colorado. The drill samples to be tested came from the interval: 13ft (4.0m) to 133ft (40.5m), an interval of 120ft (35.6m), and returned weighted average assays of 2.05 g/t Au and 2.01 g/t Ag, including 5ft (1.52m) from 119ft to 124ft (36.3-37.8m) of 42.68 g/t Au and 15 g/t Ag. These assays are significantly higher than those from the original hole 17OKC-356 (124ft averaging 0.31 g/t Au) and reflect the variable nature of gold mineralization at Kilgore. The samples, as analyzed in both holes, came from near surface, hydrothermally altered and oxidized rhyolite-composition lithic tuffs.

Metallurgical testing of the samples consisted of:

  • Initial head grade assay of each of the drill intervals submitted
  • Bench-top bottle roll leach tests
  • Column leach tests at ½-inch, 1½-inch and 3-inch crush sizes

The test work was conducted to confirm the suitability of this material to treatment by cyanide heap leaching and to validate the crush size required for efficient gold extraction. Each of the tests was conducted in a typical heap leach configuration.

The column test results indicate that a finer crush size improved gold extraction up to 1.5” with further size reduction beyond this showing additional benefit. Final gold extraction after approximately 200 days (see Figure 1) at a 0.5” crush was 92.6%, and 85.9% at 1.5”, and 56.1% at 3.0” inch crush after 120 days that was terminated when no further gold extraction was recorded. Silver extractions were 41.9%, 37.2%, and 17.4% respectively.

Table 4: Summary of Column Leach Results
Crush Size Extraction % Residue Assay Calc. Head NaCN Consumption (kg/t) Lime Consumption (kg/t)
Au Ag Au (g/t) Ag (g/t) Au (g/t) Ag (g/t)
0.5" 92.6 41.9 0.111 1.3 1.493 2.2 4.664 4.561
1.5" 85.9 37.2 0.143 1.8 1.012 1.8 3.260 1.276
3.0" 56.1 17.4 0.313 2.1 0.713 2.5 2.362 1.121

Figure 1 Au recoveries 17OKC-379 met column test 2019

Finer crush sizes improved the gold extraction rate reaching 60% gold extraction in approximately 24 days (1/2”) versus 56 days at the next coarser crush size (1.5”). The majority of silver leached in the first 25 days. Also notable was that at half inch (1/2”) and one and a half-inch (1.5”) crush gold recoveries had not plateaued after 200 days.

Mineralogical examination of higher-grade gold occurrences within the samples submitted revealed gold grains associated with Jarosite varying in size from <2 microns to 70 microns. The identification of a direct association between gold and jarosite is an important step in understanding the nature and character of mineralization at Kilgore (see Figure 2).

Kilgore Project - Drill Hole OKC17-379 Thin Section Micrographs showing Gold Occurrences

Cluster of bright Au in a matrix of Jarosite – 200X RL

Cluster of bright Au in a matrix of Jarosite – 200X RL

Several grains of bright Au in Jarosite with prismatic Quartz – 200X RL

Several grains of bright Au in Jarosite with prismatic Quartz – 200X RL

In 2018, Otis submitted approximately 1,400 kg of whole PQ core from drill hole 17OKC-379 to RDi of Denver, Colorado under the supervision of GRE of Denver, Colorado and received the results in 2019. Drill hole 17OKC-379 was a PQ twin hole of 17OKC-356 that returned 129.4 meters(m) averaging 1.66 g/t Au from 155.4 to 285.0m; including 24.4m averaging 3.45 g/t Au from 157.0 to 181.4m (note: reported widths are estimated to be 80-100% of actual true widths). These drill results come from a package of lithologies including Tertiary volcanic rocks and Cretaceous sedimentary rocks; the lower volcanic stratigraphy rocks included intensely altered volcanic rocks of indeterminate composition.

Four mineralized samples were selected from the material submitted for petrographic analysis. The work was performed by DCM Science Laboratory Inc. of Wheat Ridge, Colorado. Of the four samples, three were sourced from Aspen Formation sediments, and the other from material determined to be part of a sill, known historically as crystal tuff or andesite dike. The results of the study confirmed that the Aspen Formation rocks are siliciclastic arkosic sediments that are silicified with a significant introduction of adularia between round quartz, and sub-angular igneous feldspar grains; the primary quartz and feldspar grains have been corroded by the alteration process. Carbon / graphite is present as discontinuous strings, dust and fragments and grains are small in size (<50 microns). Gold occurs as discrete grains <15 microns in size and associated with secondary silica along crystal boundaries and with minor siderite.

The fourth sample of indeterminate lithology from the Sill Domain was identified as porphyritic igneous rock showing strong to intense quartz-adularia alteration. Optical petrology combined with trace and whole rock geochemistry has interpreted the sill material to be from a series of faulted, porphyritic andesite flows that lie uncomformably over the Aspen Formation sediments; gold occurs within the groundmass of the andesite.

Fourteen bulk samples were submitted to RDi for comprehensive metallurgical testing. Tests included Abrasion and Crusher Work Index testing, QEMSCAN and Acid -Base accounting tests, Bottle Roll Leach Tests, and eight Column Leach tests including 12.5mm (0.5") and 38mm (1.5") feed sizes. The metallurgical tests were carried out on rocks not previously submitted for testing, that is carbonaceous Aspen siltstone and shale, altered Aspen sandstone and intrusive sill material now interpreted as andesite flows.

The gold grades varied significantly from 0.2 g/t Au to 16.9 g/t Au. Cyanide soluble gold values ranged from 0.04 g/t to 1.24 g/t Au which followed the head assay results; silver was detected in all the samples tested, ranging from 0.8 g/t Ag to 6.8 g/t Ag (note: reported widths are estimated to be 80-100% of actual true widths). Gold-silver ratios are highly variable and show no significant correlation.

The bulk density test results are 2.47 for the Sill Domain and ranged from 2.99 - 2.65 for the Aspen sediments.

Crusher work index testing determined the samples to be medium- to very-hard. The Sill Domain was the softest at14.0kWh/mt. The Aspen sediments are harder at 20.3 kWh/mt. Abrasive index testing determined that the samples were abrasive to very abrasive. The Sill Domain is the most abrasive at 0.717 while the Aspen Sediments are less abrasive at 0.458.

Table 1.  Crusher Work and Abrasion Index Results
Sample CWi (kWh/metric ton) Ai (g)
Lower Aspen 20.3  - Very Hard 0.6322
Upper Aspen 15.5 - Medium Hard 0.4581
Sill Domain 14.0 - Medium 0.7171

Bottle roll leach tests conducted with individual samples of each of the 14 samples submitted indicate that the Aspen sediments have preg-robbing characteristics, even though test results reveal that organic carbon occurs only in small quantities. Initial gold extractions at a particle size of 10 mesh ranged from 7.5% to 68%. Subsequent leach tests at a particle size of 200 mesh exhibited gold extractions from 3.6% to 85.4% but were on the whole lower. Higher gold extraction was seen from two samples sourced from the upper Aspen stratigraphy; these samples also contained the highest gold grades of 8.13 g/t Au and 16.89 g/t Au respectively. CIL test work on select Aspen sediment samples improved gold extraction from 85.7% to 87.9% versus the original values of 15.0% to 31.4%.

Table 2. CIL Test Results for Aspen Samples
  Sample Particle
Size, P80
96 hr
Cal. Feed,
Au Ag Au Ag Au Ag
Lower Aspen Samples
Sample 1 200 mesh 87.2 55.3 0.46 3.0 3.60 6.7 1.953 1.406
Sample 2 200 mesh 85.7 56.7 0.54 1.6 3.78 3.7 2.133 1.515
Upper Aspen Samples
Sample 3 200 mesh 87.9 47.4 0.31 7.6 2.55 14.5 2.857 3.571

Sill Domain samples readily leached by bottle roll without the need for CIL. Each sample achieved gold extractions of 87.8% and 84.9% at a particle size of 10 mesh, while the 200 mesh grinds achieved 92.3% and 93.8% gold extraction. Silver extractions during bottle roll leaching were similar for all samples, ranging from 34.5% to 74.8%.

Column leach tests of the Sill Domain samples indicated that the material would readily heap leach. Final gold extraction at 12.5mm (0.5”) crush was 74.8% versus 83.5% at 38mm (1.5”) crush. Silver extractions were 42.8% and 29.4% respectively. The 12.5mm (0.5”) crush material leached faster than the 38mm (1.5”) crush material, reaching 60% gold extraction in approximately 12 days of leaching versus 26 days. The 38mm material leached slower, but achieved a higher overall gold extraction. Leach tests were conducted over a period of 135 to 140 days.

Column 1

Column 2

Head assay grades for the Sill Domain samples returned an average of 0.89 g/t Au however the calculated assay grades (extracted gold + residual column gold) returned 1.38 g/t Au and 1.42 g/t Au respectively. The variation between head assay grade (one assay ton with AA finish) and calculated assay grade suggests that gold may occur as coarse grains. The results from column leach tests on the 38mm crushed core show that gold recovery is slow and continues to increase up to a leach time of 107 days, again suggesting coarse grained gold. Optical petrology shows that gold grains are very small (2-15 microns), hard to find, and do not appear to reflect the calculated average grade or presence of coarse gold.

Table 3. Summary of Column Leach Results
Column No. Extraction % Residue Assay Calc. Head NaCN
Au Ag Au g/mt Ag g/mt Au g/mt Ag g/mt
1 (0.5") 74.8 42.8 0.348 5.0 1.383 8.7 2.784 1.035
2 (1.5") 83.5 29.4 0.234 8.5 1.417 12.0 2.517 0.604

Historic Metallurgy

Echo Bay – 1995/1996 Metallurgical Testing

Echo Bay Mines submitted drill core and reverse circulation cuttings to Hazen Research Inc. (Hazen) in Denver, Colorado in 1995, in anticipation of starting up a small-scale open pit heap leach mining operation on the Kilgore deposit. The material submitted was divided into three classes: oxide , sulfide  and mixed material, and each was submitted for mineral characterization studies, bottle roll studies on reverse circulation cuttings, and column leach tests on drill core samples. It was noted from mineral characterization studies that the sulfide material did not contain significant sulfides but that it was unoxidized.

The results from 96-hr bottle roll tests on reverse circulation cuttings showed that extractions by cold cyanide solution varied from 82.9% to 94.8% with little variation between the oxide, sulfide, and mixed material types, though cyanide consumption rates were significantly higher in the oxide material. It was concluded at the time that the rocks submitted showed that the Kilgore deposit may be amenable to heap leaching which lead to further metallurgical testing.

The same three categories of mineralization: oxide, sulfide and mixed, were submitted for column leach tests; the samples weighing approximately 45.3kg (110lbs.) each were crushed to 80% passing 12.5mm (0.5”) mesh and placed in 1.8m (6ft.) by 0.15m (6”) diameter columns. Column leaching used cyanide with lime to maintain high pH and the test conducted over a 60-day period. Results returned 94.3% gold recovery for the oxide , 80.8% gold recovery for mixed  and 63.8% gold recovery for sulfide mineralization.

In 1996, Echo Bay submitted 80 kg of split drill core from drill hole 95EKC-128 that consisted of mixed oxidized and unoxidized material. Head assay grades returned an average of 0.7 g/t Au for the whole sample. The sample was crushed to 80% passing 25mm (1”) mesh and placed in 3.05m (10’) by 0.15m (6”) columns; testing was conducted over a 75-day period. Results showed an average gold extraction of 85.5% after 75 days which is very similar to the shorter period (60-day) 12.5mm (0.5”) test result suggesting that maybe the Kilgore deposit ore was crush size insensitive.

An independent study in 1996 concluded that the Hazen testing had been conducted over too short a period, 60- and 75-days respectively, and did not provide for sufficient leach time. Ore porosity had not been taken into account; the suggestion was that the difference between oxide and sulfide had no relation to primary mineralogy; no significant sulfide content had been reported and the study concluded that differences are due to porosity and that gold recoveries should be higher than metallurgical testing had reported.

Otis Gold – 2010/2011 Metallurgical Testing

In 2010, Otis Gold submitted four composite samples to McClelland Laboratories Inc. of Reno, Nevada. The composites comprised three principal host rock types identified at that time from the Kilgore deposit: Aspen sandstone, lithic tuff, and felsic dike and were derived from four drill holes: 09OKC-195, -197, -205 and -206.

The calculated head grades for the four composites were: Aspen sandstone averaged 1.44 g/t Au, for lithic tuff _1 averaged 0.55 g/t Au, for lithic tuff _2 averaged 0.69 g/t Au, and the Felsic Dike averaged 1.47 g/t Au. Silver grades averaged 3.77 g/t Ag, 5.82 g/t Ag, 7.54 g/t Ag and 3.77 g/t Ag respectively.

A direct agitated cyanidation (bottle roll) test was conducted on each composite at 80% passing 10 Mesh feed size; this test was conducted to obtain preliminary information concerning heap leach amenability. The results showed that gold recoveries obtained after 96 hours ranged from 50.0% to 78.9%; silver recoveries ranged from 37.5% to 59.1%. Cyanide and lime reagent consumptions were low. 

Subsequently, column percolation leach tests were conducted on each composite at an 80% passing 12.5mm (0.5”) feed size to determine gold and silver recovery, recovery rate and reagent requirements, under simulated heap leaching conditions. Results showed that all four composites were amenable to simulated heap leach cyanidation treatment at the 12.5mm (0.5”) feed size. Column test gold recoveries obtained from the four composites were 69.8%, 57.1%, 81.0% and 85.3% respectively after 80 to 109 days of leaching and rinsing, though one composite Lithic Tuff _2 was substantially complete after 30 days. Gold recovery rates generally were fairly slow. Silver recoveries obtained from the four composites were 36.4%, 44.4%, 58.3% and 58.3%, respectively with silver grades varying between 3.77 g/t Ag and 7.54 g/t Ag.


Of note the physical characteristic show that very little “slumping” of the sample charge occurred during leaching. Sample apparent bulk densities were essentially the same before and after leaching. Also, solution requirements were fairly low to typical for finely crushed feeds. No solution percolation, fines migration or solution channeling problems were encountered during leaching. These characteristics suggest that the samples will be physically amenable to typical heap leach.

In conclusion McClelland stated that:

  • The Kilgore drill core composites were amenable to simulated heap leach cyanidation treatment, at an 80% 12.5mm (0.5") feed size;
  • Gold recovery rates generally were fairly slow;
  • Cyanide consumptions were high, but should be substantially lower in commercial production;
  • Lime additions of 2.0 to 4.5lb/ton ore were sufficient for maintaining protective alkalinity during leaching; and
  • Bottle roll tests (10m feed size) were not particularly useful for predicting column test

gold recoveries, but were effective for estimating column test lime demand.

Otis Gold - 2012 Metallurgical Testing

In 2012, a further three drill core composites were submitted to McClelland Laboratories Inc. for metallurgical testing. The objective of the testing was to determine heap leach amenability of the three composites to comparative feed sizes. Bottle roll tests were conducted for 80% passing 1.7mm feed size. Column leach tests were conducted for 80% passing 38mm (1.5”) feed size and 80% passing 12.5mm (0.5”) feed size. In addition, abrasion and work index tests on the three composites was performed.

The three composites came from whole PQ core from drill holes 11OKC-285 and -287 which were twin holes of 11OKC-258 and 10OKC-228 respectively. The composites comprised 38m (124.5ft) of oxidized lithic tuff with an average calculated head grade of 0.46g/t Au; 38.1m (125.0ft) of oxidized felsic dike, and 32.9m (108ft) of unoxidized felsic dike with an average calculated head grade of 1.15g/t Au (note: reported widths are estimated to be 80-100% of actual true widths).

Bottle roll tests showed that all three composites were amenable to direct agitated cyanidation treatment at the 1.7mm feed size. Gold recoveries ranged from 72.1% to 91.7%. Reagent cyanide and lime consumptions were low, and low to moderate respectively.

The column leach tests showed that all three composites were amenable to simulated heap leach cyanidation treatment at 80% passing 1.5” and 0.5” feed sizes. Gold recoveries for 80% passing 38mm (1.5”) feed size were 78.5% for unoxidized felsic dike, 84.9% for oxidized lithic tuff, and 71.2% for oxidized felsic dike; gold recoveries for 80% passing 12.5mm (0.5”) were 74.5%, 85.5%, and 83.3% respectively.

In conclusion McClelland stated:

  • All three core composites were amenable to direct agitated cyanidations treatment at 80% passing 1.7mm feed size;
  • All three core composites were amenable to simulated heap leach cyanidation treatment at 80% passing both 38mm (1.5”) and 12.5mm (0.5”) feed sizes;
  • The oxidized lithic tuff did not show feed size sensitivity in regard to gold recovery;
  • The oxidized felsic dike gold recovery increased with decreasing feed size;
  • The unoxidized felsic dike required a longer leach cycle than the other two composites;
  • Cyanide consumptions were generally low (≤ 1.0 kg NaCN / mt ore); and
  • Lime requirements were generally low but higher for the oxidized lithic tuff.

As with testing in 2011, the physical mineralization characteristics were the same. Importantly, hydraulic conductivities under simulated stack heights of 40m were significantly higher than equivalent solution application rates typically employed during commercial heap leaching. The composites had hydraulic conductivities of 9.79 x 10-2, 5.72 x 10-2 and 5.47 x 10-2 cm/sec respectively.

Drill Results
2019 Kilgore Drill Plan Map 322 KB
2017 Otis Drill Results Table 217 KB
Kilgore Drill Hole Plan Map 1 MB
Kilgore Drill Hole Plan Map 541 KB
Kilgore – Plan of Operation Drill Site Location Map 542 KB
Kilgore 2017 Drill Hole Location Map 433 KB
Aspen Corridor Drill Hole Location Map 389 KB
2016 Kilgore Drill Hole Location Map and Intercepts 372 KB
2016 Kilgore Drill Results Table 369 KB
2016 Kilgore Drilling Program Drill Hole Location Map 1 MB
Kilgore Target Map 2 MB
2016 Kilgore Drill Hole Location Map 1 MB
2015 Kilgore Drill Hole Location Map 1 MB
2012 Kilgore Drill Results 232 KB
Kilgore Project - Drilling Summary by Company 717 KB
Cross Sections
Kilgore – Prospect Ridge Drill Hole 190KR-381-RC 179 KB
Kilgore – Mine Ridge Drill Hole 190KR-384-RC 297 KB
Kilgore Deposit – Indicated Resource Model 672 KB
Kilgore Deposit – Au Grade Block Model 730 KB
Kilgore Deposit – Au Grade Block Model looking South 522 KB
Kilgore Deposit – Dissemination of Au grades 458 KB
2017 Kilgore Cross Section 12100N 815 KB
2017 Kilgore Cross Section 12000N 802 KB
2017 Kilgore Cross Section 11900N 830 KB
DH 17 OKC-373 Cross Section 398 KB
2017 Kilgore Cross Section 12250 N 595 KB
2017 Kilgore Cross Section 11650 N 562 KB
2017 Kilgore Cross Section 11800N 571 KB
2017 Kilgore Cross Section 12400N 553 KB
2016 Kilgore Cross Section 12600 1 MB
2016 Aspen Corridor Cross Section 12,300 N 273 KB
2016 Kilgore Cross Section 11400 1 MB
2016 Kilgore Cross Section 11100 1 MB
2016 Kilgore Section Locations 1 MB
2016 Kilgore Long Section 1 1 MB
Mine Ridge - N-S Long Section 135 KB
Mine Ridge - E-W Section 174 KB
Soil Sampling Maps
Gold Knob/Cathy Claims Geochem Block Map 469KB
2017 Otis Kilgore Regional Gold (Au) Sampling Results 1.2MB
2017 Otis Kilgore Regional Volcanic Terrace 1.8MB
2017 North Grid Anomaly Gold (Au) Results 1.5MB
2017 South Grid Anomaly Gold (Au) Results 1.5MB
Kilgore Property – Volcanic Terrace 1.38MB
June 2017 Kilgore Claim Map 6.8 MB
2016 Kilgore Property Position
Kilgore Gold Project: Geologic Map
2011 Mine Ridge and Prospect Ridge Soil Survey Results
2011 Mine Ridge and Prospect Ridge Drill Results
2011 Soil Sample Survey Map

2019 Kilgore Drill Program

2017 Kilgore Drill Program

Past Kilgore Photos