Alta Zinc has one granted Mining Concession, ten granted base metal exploration licences and six licence applications covering the Gorno Zinc Project in the Bergamo Province of the Lombardia region in northern Italy. The Bergamo region of Italy has a long history of mining extending back to the Pre-Roman (Celtic) times.
The Gorno underground zinc mine ceased operations in the early 1980s following a Government initiative for its then owner, SAMIM (a state owned company and part of the ENI group), to focus solely on oil and gas. The intrinsic mineral economics had little to do with Gorno’s premature closure, rather SAMIM was directed by the Government to divest all of its mineral projects globally and focus exclusively on oil and gas.
The Gorno deposit is a Pb-Zn-Ag deposit of the Mississippi Valley Type (MVT) and is part of an extensive series of deposits that occur across the Alps and adjacent European Platform. Historical recorded mine production from Gorno is 6Mt at an average grade of 14.5% Zn+Pb yielding high quality 55-60% Zn sulphide concentrates and 30-40% Zn oxide concentrates with low impurities.
The modern exploitation of the zinc and lead reserves at Gorno began in 1888 and were undertaken by the English company, Crown-Spelter. In 1920 the Belgian company, Vielle Montagne, acquired Crown-Spelter and continued works at Gorno until 1940. Montagne then sold the mines in 1940 to the Italian company, AMMI, who continued to work the deposit. In 1978 SAMIM acquired and conducted treatment activities until 1985 at which time all permits were relinquished.
The final period of mining activity at Gorno focused on the development of exploration drives and underground drilling well outside historical mining areas whereupon excellent intercepts of zinc, lead and silver were encountered in numerous locations, including the Colonna Zorzone deposit that SAMIM were preparing to develop before operations were prematurely closed down based on the Government directive.
The predecessor of Alta Zinc subsequently applied for exploration licenses over the area of the old mine workings. A compilation of historical data was then created from open file data including reports, geological maps, cross sections, drill logs and chemical assays sourced mainly from the Bergamo State Archive, and the Gorno Mining Museum.
In January 2015, Alta Zinc established an office in Oltre il Colle, employed local staff and appointed local contractors, EDILMAC, to rehabilitate a small part of the historic 230km of underground workings accessible from Oltre il Colle. This work provided the required access to facilitate an extensive drilling campaign for the Colonna Zorzone deposit.
The drilling has validated the historic results and provided the drilling results for the Mineral Resource estimate for the Colonna Zorzone Deposit, which is the basis of on-going studies of development options for Gorno.
The May 2017 Mineral Resource Estimate at various cut-off grades is set out in the Table below.
|May 2017 OK Estimate
Reported using various Zinc cut-off grades
Subdivided by JORC Code 2012 Resource Categories using ROUNDED figures
|Category||Cut-off Grade (Zn %)||Tonnes (Mt)||Total Zinc||Total Lead||Silver|
|Grade (%)||Metal (Kt)||Grade (%)||Metal (Kt)||Grade (ppm)||Metal (Moz)|
|Indicated + Inferred||1||3.3||4.8||160||1.3||42||27||2.9|
Gorno has the strong support of the local communities and regulatory authorities given its important history, favourable environmental characteristics and potential contribution to local employment. Alta Zinc continues to work closely with all stakeholders to re-establish mining operations at Gorno in collaboration with international financiers and off-takers.