Silver Mine - Exploration Work
After the initial discovery of the deposit in 1980, Kajaani Oy continued systematic exploration over the area. This exploration work included detailed bedrock mapping of the whole Tipas greenstone belt, extensive and systematic geochemical till sampling, extensive geophysical surveys and also numerous drill holes drilled to the most prospective areas and anomalies found during the exploration work.
Taivalhopea Joint Venture
In 1986, the claims were extended for further three years. During 1988 Kajaani Oy entered a joint venture agreement with Outokumpu Oy to form Taivalhopea JV, which was equally owned by both parties, with Kajaani Oy remaining the operator for Taivalhopea JV. In 1989, Kajaani Oy was merged into Yhtyneet Paperitehtaat Oy, and mineral rights owned by Kajaani Oy were transferred to the new company. The same year Taivalhopea JV applied for a mining concession on the basis of the surface drilling results.
After the surface exploration phase (1980-1989), the Silver Mine project moved to the resource definition and pre-production phase. Taivalhopea JV's objective was to develop underground access to the identified mineralisation and to further investigate potential exploitation of the Silver Mine Ag-Zn-Au-Pb deposit.
All diamond drilling projects have been conducted by the previous holder of the property. Some of the cores are available at the National core deposit operated by the Geological Survey of Finland.
Exploration diamond drilling undertaken by Kajaani Oy included 183 surface diamond drill holes, which extended for a total of 35,223 meters. This amount also includes regional exploration holes which do not intersect the Silver Mine deposit. The deepest surface diamond drill hole is R-126, which is 750 meters long with a -81 degrees dip. The hole penetrates to the depth of 622 meters below the surface.
The second phase of drilling conducted by Taivalhopea JV comprised 156 drill holes and a total length of 11,906 meters. All 156 holes are drilled from underground with mainly east azimuth and various inclinations (between -49.1 degrees and 75 degrees). All drill holes were drilled with ONRAM 1000 equipment owned by the operator. The core drilled during this campaign was T46 producing a 35-millimetre core in diameter.
The Tunnel Project
From 1988 to 1990 Taivalhopea JV constructed 2569 meters of the underground ramp to access the identified mineralisation and to enable underground drilling. The developed ramp extends from the surface down 325 meters below surface (+50 to +375 meters). During the development phase, a 57-meter cross cut to of the level +200, and an 86-metre access tunnel to the ventilation raise were constructed. During the Kajaani-Taivalhopea exploration phase 1980-91, 335 diamond drill holes of 46 000 m were drilled, where of 56 from the mine tunnel.
A vertical ventilation raise was developed from the level +350 to the surface. Altogether, 64 550 cubic meters of rock were excavated. From the exploration drift and the so-called ''C-ore'' between levels +325 and +355, Taivalhopea JV extracted a total of 2,000 to 3,000 tonnes of mineralized material. All mineralized material is stored on the surface in nine different piles, which are classified according to their underground location.
Final Results of the Taivalhopea Joint Venture
Mineralogical and process tests were conducted from the drill core material. Results and methods are reported in separate historical reports compiled by Outokumpu and VTT Technical Research Centre of Finland in 1985 and 1989, respectively. According to these historical reports, conventional processing methods are amenable in producing good quality silver-lead concentrate and a separate zinc concentrate.
In 1991, Taivalhopea completed the surface and underground drilling projects and compiled a mineral resource statement.
During the same year, Outokumpu Mining Services conducted a full-scale feasibility study concerning the exploitation of the Silver Mine Ag-Zn-Au-Pb deposit. The outcome was that the deposit was not economically viable due to weak metal prices and their declining forecast trend in the following years. In 1991 Taivalhopea JV put the development of the Silver Mine deposit on hold.
The main geophysical tools applied in exploration were electro-magnetics, Turam, Slingram and VLF-R methods. Ground magnetic and gravimetric surveys cover most of the area of interest. According to previous reports, the best electromagnetic response was obtained from barren pyrite-dominated horizons, and the mineralisation itself gives an only vague and ambiguous response to all geophysical methods. The most usable geophysical method is reported to be the mise-a-la-masse method, applied to connect sulphide-bearing mineralized units from drill hole to drill hole, together with IP.
An aerogeophysical low-altitude survey was conducted in 1981 by the Geological Survey of Finland (GTK). This survey included magnetic and frequency domain electromagnetic surveys together with the radiometric survey, and was flown in 200-meter line spacing. Detailed survey specifications are available at http://www.gsf.fi/aerogeo/en/index.htm. A new airborne survey was conducted by GTK in 2005, applying 50-meter line spacing and a flight altitude of 30 metres, covering the whole Tipasjärvi greenstone belt.
Geochemical surveys have been conducted in the immediate surroundings of the deposit area and its strike extensions. The main method used was percussion drill sampling, which retrieves small chip samples from the bedrock surface under the till coverage. The main sampling profiles were between 40 and 100 meters apart, and the distance between points on a line varied from 10 meters to 40 meters. Sampling profiles were oriented perpendicular to the rock association's main strike. According to historical reports, silver and lead anomalism in samples reveals the position of the current deposit accurately.