Rosita Mining Corporation: Santa Rita Project - Updated Metallurgical Results

Summary

In previously reported test results announced on September 21st, 2016, it was concluded that recoveries of gold by cyanide leaching from ground material was more than 90% from the stockpiles and 80% from tailings. 75% gold was recovered from coarser material. Copper recovery from cyanide leaching into solution was 35%.

The next stage of testwork reported here, was designed to test the recovery of copper and the recovery of cyanide from these leach solutions via the SART (Sulphidization, Acidification, Recycling, and Thickening) process

This SART testwork, has been very successful and is appropriate metallurgically for the Project:

-The leached gold can be recovered onto carbon in the normal way. An overall recovery of gold from Stockpiles and Tailings is 80-85%

-99% of the copper in the cyanide solution can be recovered as Copper Sulphide concentrate.

-The cyanide consumption to maximize the dissolution of the gold will be 2.4 Kg /t, much lower than the previously reported leach testwork.

-Acid leach of the gold leach tailings showed further copper recovery of 34%, thus total copper recovery 65-70% may be estimated

John Cook the CEO of Rosita stated that the successful SART testwork is very positive news for the Project. It has consolidated the cyanide gold recoveries shown by previous work. Overall copper recovery will be higher than a simple acid leach. Significant cyanide recovery has been demonstrated resulting in a modest cyanide consumption. The significant gold and copper resources in the stockpiles and tailings resources announced on February 8th, 2016, can be recovered in a simple way.

Previous testwork

The high cyanide consumption of 8.82 kg/T and 4.46 kg/T reported in the previous press release was due to the requirement to maximize the copper soluble dissolution and improve the kinetics of the gold leaching. In both cases, 60 % of the cyanide consumption was due to the copper complexing with the cyanide which is expected to be recoverable, along with the copper using SART technology. High recoveries of gold and copper were demonstrated.

Updated Test Work

The SGS testwork protocol described below is standard; it mimics the conceptual flow sheet that was devised from the initial SART testwork done for this project at SGS. (see figures 1 and 2) It involves standard process equipment using the standard gold and copper processing reagents.

Figure 1

Click Image To View Full Size

Figure 2

Click Image To View Full Size

The solutions from the leach tests were used for SART testing for recovery of cyanide from the copper complex, precipitation of copper and recycle of solution into ongoing cyanidation leach testing. A series of four (4) SART tests were carried out to test Acid addition pH rates, Sodium hydrosulphide (NaHS) stochiometric addition rates, recycle leaching to feed material, and also subsequent carbon loading rates.

The resultant optimized SART work is as follows (pH 4 and 100 % NaHS stochiometric addition rate) :

-Free Cyanide (CNF) increased in the leach solution from 1220 ppm to 2520 ppm

-Copper was reduced from 1660 ppm 15.4 ppm with 99.1 % copper precipitation.

-Gold in solution was 0.33 ppm - 0.34 ppm after SART and copper precipitation with carbon adsorption of 2 kg/ml.

-The resultant barren solution from the SART process was recycled for leaching of the stockpile ore with additional cyanide that resulted in 95 % Au recovery and 36 % copper recovery (excluding residual gold from the SART return stream).

-The calculated cyanide added and consumed for gold dissolution was 2.41 kg/T

A single leach test to examine the amenability of the cyanide residue to copper extraction through sulphuric acid was carried out. After only 24 hours of leaching, a copper recovery of 34 % was obtained.

In general, the testwork has demonstrated that the SART process is appropriate for this project metallurgically for the Santa Rita material with solutions containing recoverable gold and copper.

Next Phase Testwork

The final ground tailings from the stockpile and tailings stockpiles leached material will be comingled with the screen +1/4-in. feed material to undergo column heap leach simulation. The work will commence shortly with completion in Q1 - 2017. The gold and copper recovery for this process is essentially known.

The test campaign underway at SGS Lakefield will be complete in Q1-2017 and the final SGS report will follow and used as the metallurgical basis for more detailed engineering.

The current testwork and engineering information together with local costs for labour, power, reagents, and rock moving have allowed the work plan for the environmental permit to begin..

This will join baseline work that has been ongoing at site for the past three months.

About Rosita Mining Corporation

Rosita is a junior mining and exploration resource company focused on growing shareholder value through the development of near-term mining projects and advancing accretive exploration opportunities.

Rosita and Calibre hold 65 % and 35 % interest respectively in the Rosita copper-gold-silver supergene/skarn/porphyry project in Nicaragua located 275 kilometres northeast of Managua.

Qualified Persons

David Salari, P.Eng. and John Cook, MIMMM, Qualified Persons, as defined by NI-43-101, have read and approved the contents of this press release.

Copyright (c) 2017 TheNewswire - All rights reserved.