United States Antimony Reports the Successful Start Up of Los Juarez Gold and Silver Production

HIGHLIGHTS

  1. The initial cyanide leach recoveries of the Los Juarez gold and silver have been successful.
  2. Minor changes in the cyanide circuit have been made and will further enhance recoveries.
  3. The overall Los Juarez recovery involves utilizing caustic and cyanide leach circuits.
  4. The startup and use of the cyanide leach could result in gold values that are greater than the global average ore grades. More production this year will verify final global estimates.

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Thompson Falls, Montana. United States Antimony Corporation (“USAC”, NYSE American “UAMY) reported that the initial production recoveries of the Los Juarez gold and silver cyanide leach plant are successful.

USAC began exploration, development, mining and milling of the Los Juarez deposit in 2006. Detailed mapping and sampling delineated jasperoid silica-rich mineralized pipes over an east-west strike length of 3.5 kilometers with a maximum width of 1 kilometer.

After years of metallurgical work, permitting, and construction, the Company has established the following processes to maximize recovery:

Process chart

LOS JUAREZ MINE

Preliminary exploration indicates that it is a deep-seated silica-rich jasperoid with the following global assays and inferred recovered grades:

MetalAssayRecoveryRecoveredValueValue
Gold0.035 opmt90%0.0315 oz$1,600/oz$49.60
Silver3.27 opmt85%2.7795 oz$18.00/oz$49.86
Antimony0.652%70%10.06 #$3.15/#$31.69
Total$131.15

Global assay results and exhaustive metallurgical work have indicated a ratio of approximately1 ounce of gold to 90 to 130 ounces of silver. The bulk of the gold appears to be not homogenous or recoverable by flotation. The problem is that the gold may be coarse, not liberated from the gangue, or associated with oxide minerals that are not amenable to flotation. Accordingly, the gold may be of a higher grade. The variation in gold grades is illustrated in the following shallow drill holes:

HoleInterval
meters
Gold
opt
Gold
g/t
Silver
opt
Silver
g/t
Antimony
%
LJ81.5-30.2688.336.17191.890.280
LJ83-4.50.71222.147.75241.030.235
SJ230-10.0100.3110.5326.61.19
SJ310-.8<0.002<0.0614.5451.00.853
SJ360-1<0.002<0.066.88214.00.571
SJ380-1<0.002<0.064.02125.00.445
SJ510-1.20.1685.2252.4676.50.0930
SJ540-10.44813.933.52109.50.106
SJ541-20.1865.7852.4174.950.0681
SJ54A1-20.1745.4111.9055.10.0856
SJ54B0-10.81225.2532.0664.10.9068
SJ54B1-20.65020.2152.3573.090.0800
SJ54C0-10.2768.6390.84426.250.1130
SJ54C1-120.47614.8042.4074.640.0985
SJ54D0-10.2367.3400.70621.960.0788
SJ54E0-10.1825.6600.2186.780.0415
SJ54G0-10.32610.1390.43813.620.107
SJ560-10.50015.553.73116.00.274
SJ561-20.43613.5603.89120.980.256
SJ56A1-20.1103.4213.78117.60.0811
SJ56D0-10.1765.4740.9429.20.126

FLOTATION MILL

The recovery of precious metals in the flotation concentrate was poor. The typical gold recovery was less than 25%, and the silver recovery was less than 70%. Antimony recoveries have generally been less than70%, but they are expected to increase when mining is below the surface oxidized zone. Since the silver is associated with the antimony, the silver flotation recovery is also expected to increase with depth.

FLOTATION MILL CONCENTRATES AND CAUSTIC LEACH

Generally only 30% to 40% of the gold and silver was recovered from the flotation mill concentrates by the USAC proprietary smelting process. This problem was solved by leaching the antimony out of the concentrates with a caustic leach and resulted in nearly a 100% recovery of gold and silver from the concentrates.

FLOTATION MILL TAILINGS AND CYANIDE LEACH

The flotation tailings that contained up to 75% of the gold and 30 to 40% of the silver are taken to a carbon in cyanide leach circuit (CIL). Some seven leaches have been completed. The gold recoveries have been in the 86% range, and the silver recoveries have been lower. Overall recoveries of gold and silver are being enhanced by circuit modifications to achieve a gold recovery of 90% or better and a silver recovery to 85%.

REFINING

The precious metals are concentrated in the Montana refinery and sold in the United States.

ANTIMONY & ZEOLITE

Production during the month of February was as follows:

ProductFebruary 2020 sales
Antimony pounds114,428
Zeolite short tons942

From the middle of January 2020, the Rotterdam price of antimony increased from $5,700.00 per metric ton or $2.585 per pound, to $6,400.00 per metric ton or $2.903 per pound. This is an increase of $0.318 per pound which should impact our sales in the future. Antimony prices have climbed in the past several weeks due to production curtailments and supply restrictions related to the ongoing Coronavirus (COVID-19) epidemic in China. The Company has been approached by several customers seeking new and diversified supplies of antimony products.

CEO John Lawrence said “The initial trials of the cyanide leach circuit for Los Juarez have been a success. We intend to have further details on estimated grades as production is ramped up. Proceeds from the 100 ton per day pilot will be used to complete the installation of the 400 ton per day mill.”