Operations

Drumlummon

The Drumlummon operation was formerly owned by RX Gold & Silver prior to the merger with US Silver in 2012.

The Drumlummon Mine Property is located approximately 25 miles northwest of Helena, Montana, and is within the Marysville Mining District, Lewis and Clark County. Prior to the 1980s, the Marysville District was the primary hard rock gold producer in the State of Montana and the Drumlummon Mine was the largest operation within the district.

 

The Drumlummon Property is comprised of over 350 unpatented claims, covering over 5500 ac, and 51 patented claims, covering approximately1094 ac. Of the patented claims, six parcels, totalling 30 claims and covering approximately 243 ac are from the Drumlummon Claim Group.


The Drumlummon mine consists of a "bonanza" style epithermal deposit which is characterized by very high grade gold and silver. Drumlummon is a high grade underground mine with extensive infrastructure from past production and recent development.

Drumlummon has historically produced over 1 million ounces of gold and 12 million ounces of silver.

Given the weakness in gold prices and mine performance, production at the Drumlummon Mine near Helena Montana was discontinued and the mine was put on care and maintenance in Q2 2013. 

Recent History

In 2007 and 2008, the RX Exploration (RX) rehabilitated the 400 foot level in preparation for underground diamond drilling which commenced in the spring of 2008 and continues today.

In November, 2008 the RX released its first resource estimate from the underground core drilling of the newly discovered Charly Vein, located east of the old workings.

Drilling continued during 2009 on the Charley Veins and in an area of the former workings on the Drumlummon Vein known as D Block. Throughout 2009 the RX reported the results of underground drilling and confirmed significant gold and silver values remain in the hanging wall and footwall of the old workings with mineralized intersections of up to 32 feet, gold values of up to 5 ounces per ton ("opt") and silver values of up to 149 opt

Bulk metallurgical test work was conducted in 2010 at a contract mill facility located approximately 110 miles away in Philipsburg, Montana, which showed recoveries exceeding 92% for gold and 87% for silver. In June and July  2010 the RX produced Approximately 2500 ounces of gold and 55,000 ounces of silver by milling an average of between175 and 180 tonne per day under the test milling program.

In November, 2010 the company announced the start of a new decline from an existing portal (The Maskylene Tunnel) on the northern slope of Drumlummon Ridge. In May 2011 RX completed a second access (the Gunsinger Decline) which joined the existing workings to surface. This decline established a second, larger route into the mine that will allow the entry of larger mechanized equipment, provide a second haul route for removal of ore and waste from the mine, and promote increased airflow for mine ventilation.

The decline was driven from an external portal established 1,250 feet east and 70 feet lower than the Maskelyne Tunnel, which had previously been the only accessible mine entry. Work advanced from both ends of the decline/tunnel, with one excavation team working from the external portal and the other team working from the internal ramp (collared on the 400 level, south of the #1 shaft).

Using this new access the mine began test mining in the fall of 2011 on the Charly Vein and on areas of remaining mineralization in the main Drumlummon Vein. The ore was trucked to the leased mill facility in Phillipsburg for processing.  Test Mining continued at a rate of approximately 300 tons per day in early 2012 with full production reached by Q1 2012.

In Q2 2013 the Drumlummon mine was put on care and maintenance due to weak commodity prices and performance.

Geology and Mineralization

The deposit is hosted by the Cretaceous Marysville stock and metamorphosed Precambrian sediments. The mineralization occurs as quartz fissure veins and silicified breccia in structures focused along the eastern margin of the stock. The primary ore minerals are native gold and silver sulfosalts.

The Marysville mining district produced over 1 million oz. of gold between 1873 and 1920 and the principal precious-metal vein system of the district is centered at the Drumlummon Property. In the region, Precambrian crystalline and metasedimentary rocks form the basement and range in age from approximately 1.6 to 3.27 Ga. Middle Proterozoic Belt Supergroup rocks unconformably overlie the basement rocks and form the main exposures in the Marysville area. These rocks are cut by Late Cretaceous intrusive related to the Boulder Batholith comprised of quartz monzonite or granodiorite and included the Marysville Intrusive in the mine area. Late Cretaceous dacite, rhyodacite, and quartz latite volcanic rocks cogenetic with the Boulder Batholith, and locally forming roof pendants in the batholith are seen in the western part of the Marysville area. Tertiary (Eocene-Pliocene) volcanic rocks are predominantly quartz latites and rhyolites. The Tertiary and Quaternary sediments and volcanic rocks are postorogenic and are thickest in local Cenozoic basins.

 

The Late Cretaceous Boulder Batholith and the rocks of the synorogenic thrust and fold belt of Montana host one of the country’s major mining regions. Gold, silver, copper (Cu), and lead (Pb), have been produced from over 30 mining districts. The majority of these deposits are fissure veins, but skarns and disseminated deposits related to the intrusive rocks are locally important. Fractures hosting the majority of the mineralized veins were formed by regional east-west compressive stress during the Late Cretaceous and Early Tertiary. The widest and longest veins regionally are oriented east-west and are extensional fractures that are parallel to the principle compressive stress axis. Veins sets trending northwest and northeast of which the Drumlummon Main veins and other veins in the Marysville area are typical, formed as steeply-dipping conjugate shears. North-trending fractures and veins formed late as release fractures oriented perpendicular to the applied stress. The latter are not common, nor are they typically mineralized.

 

The main lithological units of the Precambrian Belt Series that are found locally within the mine area are the Empire Formation, Helena Formation, Mount Shields Formation, and Intrusive Rocks. The main mineralized veins in the Property are the Drumlummon, Empire, Frankie, North Star, Castletown, and Charly, but there are many other veins in the district that have undergone various amounts of mining. The D Block, D Block South, Jubilee, Christmas, Pixley are known ore shoots in the Drumlummon Vein.

 

In March 2012 a NI 43-101 Resource was prepared by Wardrop TetraTech for the Drumlummon Mine focusing on the Charly and Christmas Veins and the D-Block of the Drumlummon Vein.  Below is a summary of the resource using a 0.1 ounce per ton gold equivalent cut-off. Click here to view the NI 43-101 Technical Report.

 

Cut-off

Tonnage

Metal (ounces)

Grade (ounces per short ton)

 

Au_Eq

Short tons

Au_Eq

Au

Ag

Au_Eq

Au

Ag

Measured

0.1

14,351.1

9,307.6

6,992.1

152,170.8

0.649

0.487

10.603

Indicated

0.1

161,129.6

43,473.4

36,966.9

427,595.5

0.270

0.229

2.654

Inferred

0.1

164,371.5

45,316.1

39,675.1

370,713.9

0.276

0.241

2.255

Measured + Indicated

0.1

175,480.7

52,781.0

43,958.9

579,766.2

0.301

0.251

3.304

 



Notes:

1. “Au eq oz” – Gold equivalent measured as the combination of reported gold and silver. Gold price is calculated as $1,450 oz./T and silver as $24.00 oz./T.

2. The information provided in the Resource Estimate was prepared by Dr. Robert Morrison P. Geo. of Tetra Tech Wardrop who is an independent Qualified Person as defined under (NI) 43‐ 101. Dr. Morrison has reviewed and approved the contents of this news release that relate to the Resource Estimate.

3. Resources were estimated using Datamine software from data provided by RX using a three dimensional block model (5 feet by 5 feet by 20 feet).

4. Data verification was undertaken by Wardrop staff prior to development of the block model.

5. The gold equivalent resources were calculated using a $1450 gold and $24 silver price.

6. The main structures that host the mineralized veins were interpreted as a three dimensional wireframe domain. These were used to estimate resources and constrain grades.

7. Interpolation parameters were derived on geostatistical analyses conducted on 3 foot composite drill‐hole data. Block grades have been estimated using “Ordinary Kriging” interpolation method and the mineral resources have been classified based on proximity and continuity of mineralization in accordance with CIM best practices.

8. Mineral resources, which are not mineral reserves, do not have demonstrated economic viability. The estimate of mineral resources may also be materially affected by environmental, permitting, legal, title, taxation, socio‐political, marketing or other relevant issues. These mineral resource estimates include inferred mineral resources that are normally considered too speculative geologically to have economic considerations applied to them that would enable them to be categorized as mineral reserves. Even though evaluation mining has been undertaken in areas of the Drumlummon Mine with M&I class mineral resources there is no certainty that inferred mineral resources will be converted to measured and indicated categories through further drilling, or into mineral reserves, once economic considerations are applied.

Mr. Jim Atkinson, P. Geo. is the qualified person responsible for preparing scientific and technical information that is posted on this website.
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