It’s one of the most prolific mineral districts in the world with a history pre-dating Roman times, yet, until recently, few people knew much about it. And that low profile allowed Frank Timis, chairman and founder of
“RTZ, BHP, Normandy… they’re all here,” Timis told The Northern Miner and a group of mining analysts during a tour of the company’s main projects in his former homeland. “Newmont and Ashanti have ground near ours, and Barrick Gold and Placer Dome are looking around.”
The majors came for the same reason Gabriel did: the Golden Quadrilateral offers potential for bulk-tonnage gold deposits, and in a region that welcomes and needs mining investment. As a bonus, the area hosts numerous base metal deposits, including bulk-tonnage porphyry copper deposits of the type to attract producers such as Broken Hill Proprietary, plus waste dumps and tailings with grades of economic interest.
Gabriel’s most advanced project is Rosia Montana, 85 km north of Deva. A prefeasibility study on the Cetate and Cirnic deposits, which together host the bulk of resources at Rosia Montana, is expected in November. The long-term goal is to develop a modern mining operation encompassing the same ground worked by the Romans almost 2,000 years ago, by local miners in the medieval period, by the Austro-Hungarians before the First World War, and by communist Romania in the latter half of this century.
Attracted by placer gold in local streams and rivers, the Romans began mining in 131 AD, both from surface and underground. They later occupied the region, giving Romania its status as a Latin nation surrounded by Slavic peoples.
The Roman-era workings consist of surface pits and underground glory holes, locally called Coranda, which exploited higher-grade quartz veins and high-grade portions of the breccia pipes at Cetate and Cirnic. Most of these openings have since collapsed, owing to the fact that they were driven into softer ground than the more recent workings.
The district reached peak production during the Austro-Hungarian empire, resulting in the development of several hundred kilometres of underground openings covering a vertical range of about 400 metres. They are in remarkably good condition, except for the openings, which must be re-timbered before entry.
Whereas the Romans and Austro-Hungarians chased high-grade veins, Gabriel has focused its exploration efforts on the disseminated inter-vein material — the host rock — which is well-mineralized over broad areas, albeit at lower grades than the veins exploited in the past.
Despite all the past mining at Rosia Montana, the project appears to offer plenty of potential for a large-scale, open-pit mine. It hosts a resource of 144 million tonnes grading 1.7 grams gold and 10 grams silver per tonne (7.7 million contained ounces gold and 44.3 million contained ounces silver), based on a cutoff grade of 0.8 gram gold and a 10-by-10-by-10-metre block size. If a 1.2-gram cutoff grade is used, the number of contained ounces drops to 6 million for gold and 30.8 million for silver.
“There aren’t many deposits of this size that don’t already belong to a major,” Timis told analysts, hinting that Gabriel might vend its multi-million-ounce project when the time is right.
“We’ve had numerous majors on the property in the past year,” he added. “But we’re not interested at this stage. We’re still expanding the known mineralization and we still have to do infill drilling to convert resources to reserves.”
Once the prefeasibility by Pincock Allen & Holt is completed, later this fall, Gabriel will be allowed to increase to 80% its current 65% interest in the 21.2-sq.-km exploitation concession (held by Romanian company Euro Gold). The remainder will be retained by joint-venture partner Minvest, a state-owned mining company, though Gabriel has a pre-emptive right on this 20% stake.
Minvest currently operates an open-pit mine that produces about 12,000 oz. gold annually in the Rosia Montana concession. However, the operation suffers from a variety of problems typical of state-owned mines, including poor grade control and high dilution, inefficient mining techniques and low recoveries. The antiquated mill recovers only about half the gold from ores processed in its flotation circuit, and, if that weren’t bad enough, the nearby smelter doesn’t do much better when it processes the concentrates.
Mihail Ianas, president of Romania’s National Agency for Mineral Resources, resources, said the government has closed numerous mines in the country for similarly bleak operating efficiencies. “We’ve been spending two dollars to make one, and we can’t afford to continue doing that,” he said. “That’s why we’re welcoming foreign investment and trying to continue our privatization process.”
In the past two years, Gabriel’s exploration expenditures have amounted to about $15 million, much of which was directed at Rosia Montana. The initial resource estimate of 1.9 million contained ounces, reported early this year, grew to 5.4 million by June, and then to 7.7 million in mid-September, where it currently stands.
The latest resource estimate is based on 14,646 metres of reverse-circulation and diamond drilling in 85 holes and 7,700 metres of underground channel sampling at the Cetate deposit, as well as 28,040 metres of underground channel sampling on 16 underground levels at Cirnic and the smaller Cirnicel deposit (about 185,000 contained ounces). The calculations were made by Gabriel’s geological consultant, Resource Service Group of Australia, and are based on that country’s AusIMM/JORC guidelines.
An updated resource estimate will follow early next year, and speculation already is growing that the number may top 10 million contained ounces. While counting ounces before they are hatched isn’t popular with regulators these days, the predictions don’t seem outlandish when applied to the deposit type, the results achieved to date, and the fact that the mineralization remains open at depth and in several directions.
“Our discovery cost is less than US$2 per oz.,” Timis said.
While this figure obviously reflects development work by previous operators, Gabriel has benefited in other ways from the extensive underground workings below its proposed pits. Good ground conditions have allowed the company and its consultants to carry out extensive channel-sampling on most of the drives and crosscuts.
Under the supervision of Resource Service Group, continuous 1-metre channel samples are collected from all the accessible and safe workings in the deposits. Duplicate samples are taken every 20 metres. The process is akin to drilling vertical holes, though the cost is considerably lower. A geologist is always present to verify the sampling process and log the samples according to geology and structure.
The mineralization remains open at depth below the Cetate and Cirnic deposits, to the southwest and to the northwest, where areas of higher-grade mineralization have been found.
In the coming months, drilling will test the extent of mineralization at depth under Cetate and Cirnic, and areas of higher-grade mineralization (for example, 1 metre of 46 grams, 1 metre of 77.2 grams, 2 metres of 52.1 grams and 1 metre of 44.5 grams) identified at the nearby Igre-Jig-Vaidoaia prospects. Also, underground infill drilling will attempt to convert resources into reserves — a step that will be cornerstone of the final feasibility study. At present, only about 2.5 million contained ounces are classified as measured in the existing resource.
Geology
Gabriel’s exploration programs are managed by geologist Steven Bugg, who previously managed Barrick Gold’s exploration efforts in Indonesia. With so many prospects to test
, his challenges at Rosia Montana appear to be mostly pleasant ones. His crews are still finding mineralization between the Cetate and Cirnic pits, as well as areas of higher-grade mineralization (4-5 grams or more) in nearby prospects. And Bugg is particularly keen to drill the deposits below existing workings to a vertical depth of at least 600 metres, where, he suspects, grades will improve.
The geology of Rosia Montana consists of dacitic, sub-volcanic intrusions emplaced into a sequence of Cretaceous sediments. Andesitic agglomerates have also been mapped, and mineralization is strongly associated with a series of diatreme breccias. Current thinking is that the mineralized district hosting the known deposits at Rosia Montana represents a collapsed caldera.
Three main types of breccia have been mapped: dacitic, mixed and black. The first two are mineralized; the last typically is not. The deposits are surrounded by a zone of intense hydrothermal alteration, dominantly argillic alteration and silicification. Mineralization is also hosted in the sediments.
The gold-silver zones are epithermal-to-mesothermal, low-sulphidation systems. Deleterious elements such as antimony, arsenic and telluride minerals are not believed to be present in appreciable levels.
The mineralization at Rosia Montana, whether in dacites or hosted by sediments, is controlled entirely by intense fracturing. “Where you get fracturing, you get grade,” Bugg said.
On the metallurgical front, preliminary tests have shown that up to 60% of the gold can be recovered in a gravity circuit. Various tests have been performed to date, with the best result (99%) obtained from pressure oxidation prior to cyanidation (though the cost of an autoclave circuit may be prohibitive). The favoured flowsheet option — gravity, flotation of sulphides and cyanidation of the flotation concentrate in a carbon-in-pulp circuit — is expected to be in the low-to-mid-80% range. More tests are planned.
On the mining side, the known deposits at Rosia Montana occur in silicified hills, which means a future operation should benefit from a low stripping ratio, estimated at about 1:1 waste-to-ore. In essence, mining here will be a simple case of removing small hills and working down to the valley floor or below.
Local villagers have farms in the region, some of which will have to be relocated in order to accommodate the proposed open pits. Gabriel has agreed to seek the consent of these villagers and relocate them in accordance with World Bank standards.
“Relocation shouldn’t be a problem if done correctly,” the minister said. “In the past, when [former Romanian president/dictator Nicolae] Ceausescu wanted land for some purpose, he forced people off their farms into crowded apartments. The villagers are still afraid of that, but I think they would be quite happy to move into homes with running water and better amenities.”
Other projects
On the exploration front, Gabriel has five main projects it hopes to advance in the coming years. Chief among these is Certej, a gold project, where a resource estimate by Resource Service Group is expected shortly.
Situated 15 km southeast of Deva, the 80-sq-km exploration concession contains plenty of evidence of ancient mining activity, including vertical mine development.
While Minvest operates a small, open-pit, lead-zinc mine (400,000 tonnes per year) on the concession, the land package is viewed as prospective for bulk-tonnage gold deposits.
Both vein-hosted and disseminated mineralization have been identified at Ceretej. Eight known deposits have been identified in a structural corridor. Mineralization is believed to be associated with andesitic intrusions.
Minvest and previous operators tested samples for gold and silver using the standard Romanian gravimetric assay method. However, comparative assaying of samples using fire assay with an AAS finish has found that the gravimetric method returned substantially lower grades, particularly for lower-grade samples. Accordingly, Gabriel and Resources Services opted not to use any of these assays in their forthcoming resource estimate.
Assays are now done at a new laboratory built close to Rosia Montana. The lab is managed and operated by Analabs, an Australian company with international accreditation.
Gabriel’s work at Certej has focused on underground channel sampling using existing drives. This work has delineated significant gold-silver (with or without lead-zinc mineralization) over a strike length of more than 4 km and a vertical depth of at least 200 metres. The mineralization is open in all directions.
Gabriel’s other projects in Romania include the following:
- Bucium, which contains a large porphyry copper-gold deposits on which an underground sampling program is under way. (Mining was scheduled to begin in 1989. However, these plans were put on hold after the 1989 revolution.) The concession is also prospective for epithermal-mesothermal gold-silver deposits.
- Zlatna, which hosts several epithermal gold-silver deposits and at least one known major porphyry copper-gold deposit. (No work, other than data compilation, has been done to date.)
- Bolcana, which hosts a porphyry copper-gold deposit with extensive underground workings and an associated vein-swarm deposit.
- Baita-Craciunesti, an exploration concession hosting a gold-vein system with extensive underground workings.
In the fall of 1997, Vancouver-based
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