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Metallurgical Studies 2019

Core Drilling Program

 

Four core holes were drilled as a test to compare the advantages and disadvantages with the reverse circulation (“RC”) drilling method used to date. Information obtained from the core holes confirmed the highly mineralized and structurally complex nature of the small area tested, with all holes intersecting broad zones of disseminated / stock work, oxide gold mineralization hosted in tuffaceous volcanic rocks.

 

In all three core holes that “twinned” RC holes, intervals of fine grained, low-grade gold mineralization showed reasonably good correlation between drilling methods, but higher-grade assays were not consistently comparable. Hole PC18-04 was drilled as a ‘step out’ into a previously untested structural target and intersected a broad zone of low-grade gold mineralization with higher grades up to 5.81 g/t Au over 1.7 m. As a subsequent check, cyanide shake assays and metallic screen analyses were conducted on select samples from the core holes and showed a good correlation with the initial fire assay results.

 

 

The highly fractured nature of the mineralized zones and variable core recoveries made it difficult to make direct comparisons of higher gold assays between the two drilling methods, it is also possible that the differences observed are simply due to an inherent variability in the mineralization itself. From this small test program there is no obvious conclusion that the RC drilling was under-reporting gold sample grades. Consequently, the Company plans to continue with reverse circulation (RC) as the primary and less costly method for future drilling programs, using core only in those areas where additional geological information is required.

 

Preliminary Gold Extraction Testing – Screen Test

 

A preliminary screen test has successfully produced a concentrate assaying 26.530 grams gold per metric tonne (g/t Au) from sampled mineralization with a head grade of 4.291 g/t Au.

 

The original sample was dry screened, with no crushing, into two size fractions - a coarse fraction (+95 mm) and a fine fraction (-95 mm). The two fractions were then submitted to an assay lab for analysis. The coarse fraction assayed 1.020 g/t Au and contained only 20.72% of the gold in 87.18% of the sample volume, while the fine fraction assayed 26.530 g/t Au, representing 79.28% of the gold, in 12.82% of the original sample weight.

 

The implications are that by implementing simple, low cost screening and concentrating approximately 80% of the gold in less than 13% of the material weight, it may be possible to eliminate a crushing circuit altogether, to mine large volumes of low-grade mineralization, and substantially reduce the volume of material to be processed and associated costs thereof. Furthermore, it indicates the potential to deliver higher grade feed to a processing facility, thereby allowing more intense treatment of higher grade material, which could result in higher extraction and recovery rates.

 

 

Preliminary Gold Extraction Testing – Bottle Roll

 

Bottle roll metallurgical leach tests achieved gold extraction of 97.1%, 88.5%, 96.0% and 73.6% on four composite samples with respective Calculated Head Grades (see definition in footnotes to table below) of 79.4, 0.26, 1.49 and 0.53 grams gold per metric tonne (g/t Au) from the Pamlico Project. The four samples were composited from stored coarse rejects of reverse circulation (RC).

Highlights:

  • High gold recovery, ranging from 73.6% to 97.1%, across all grade ranges
  • Rapid leach time confirms the majority of gold at Pamlico is very fine grained, going into solution readily under ordinary metallurgical conditions
  • High gold recovery confirms complete oxidation of system and lack of “encapsulation” of gold by other inert minerals such as silica or sulfides
  • Extremely low reagent consumption indicates mineralization contains little or no cyanide consuming minerals (cyanocides) or other deleterious material
  • Extended leaching time will likely improve the 97.1% gold extraction of the 79.4 g/t Au Calculated Head Grade in composite P17-10 because this composite was still yielding gold when the leach was terminated
  • For the three lowest grade composite samples, the average grade of the gold actually recovered by leaching (from Calculated Head Grades) was 27% higher than the Predicted or Assay Head Grades, suggesting both better grades, larger volumes and therefore more gold may be present in the large clouds of stock work or disseminated mineralization surrounding the structurally controlled high-grade gold at Pamlico

 

 

Preliminary Gold Extraction Testing – CN Shake Assaying

 

The results of 239 samples submitted for cold cyanide (CN) shake assaying indicate that the metallurgical response of gold mineralization at Pamlico is independent of location or depth and does not exhibit any adverse “refractory” characteristics. The samples selected are all Reverse Circulation (RC) drill samples. Of the 239 samples 40 were 0.76 meter long and 199 were 1.52 meters in length. All samples were of pulps that had previously been assayed by fire assay.

 

These results indicate that the gold in mineralization containing less than 4 grams per tonne gold (g/t Au) can likely be efficiently recovered using heap leach extraction while higher-grade mineralization should also be evaluated for conventional milling, which typically yields much higher recoveries than heap leaching. The high extraction of gold in the CN shake assays is consistent with the observed very fine grained “micron” and oxidized nature of gold mineralization at Pamlico.

 

The greatest variation in extraction appears to be grade related. The lowest grade samples as determined by fire assay: 0.003 - 0.12 g/t Au, returned an average of 315% of the fire assay grade. Obviously, it is impossible to achieve more than 100% recovery by any method. The results for the sub 0.12 g/t Au grade samples really mean the fire assays underreported the actual contained gold for samples in this grade range and that there is a potential for a lot more gold in this range than has been reported by fire assay. Samples assaying from 0.13 to 4.0 g/t Au returned an average extraction of 93.8% and extraction for samples assaying more than 4.0 to 340.9 g/t Au averaged 61.2%.

 

 

 

 

 

 


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