The Rich Gulch Project
The Rich Gulch Project is located on the Califomia Mother Lode 22 miles west of Quincy in Plumas County, northem Califomia. The property is located within the Plumas National Forest in rugged, forested terrain at an elevation of 4000 feet A recent fre has destroyed the forest covering a large area that includes the RGP mine. Highway 70 and the railroad are 2 miles distant and an improved dirt road passes through the RGP and neighboring Virgilia properties.
In 1850, during the Califomia Gold Rush, placer gold was found at Rich Gulch, a drainage which cuts across the main Mother Lode structural zone. Most of the placer gold was found in an area overlying the present-day Virgilia property, which is 2000 feet southeast and on strike with the RGP Exploration of underlying quartz veins began in the 1870's with rnost development directed at vein exposures on the RGP property. Homestake Mining Company evaluated the properties between 1927 and 1930. Tunnels on the RGP were expanded and several diamond drill holes were completed. The drilling confimmed the vein system extended from outcrop to at least 1000 feet down dip A fire destroyed Homestake's hoisting plant in 1930, leading to the temmination of the exploration program. Drifting on the English Tunnel by Homestake at the RGP mine confirmed "a good body of ore averaging 0.198 ounces gold per ton". A total of 1,032 channel samples collected from the RGP workings during 1929 and 1930 averaged 0.11 opt. Assays of up to 11.0 opt were recorded but were not included. In 1932, the Virgilia mine was put into produchon by the Virgilia Mining Corporation with support from Consolidated Goldfields and produced an estimated 320,000 tons averaging 0.22 opt gold (70,400 ounces), about 50% higher than historic underground Mother Lode producfion. There is no record of producfion on the RGP property. The mines were closed at the beginning of WWII and riever reopened. The RGP property contains no evidence of past mining except portals at the English and Blacksmith tunnels.
Both properties lie along the same mineralized zone, a felsic volcanic flow within the Triassic Cedar Fommation. The Melones Fault, the main structural feature of the Mother Lode, parallels the deposits 550 feet to the west. The fault and hanging wall rocks strike roughly 35 degrees northwest and dip 55 to 70 degrees northeast. The felsic horizon is variably mineralized with thin mesothemmal quartz veins, sheeted zones, and massive silicification. Gold is present witbin sheared sections that contain up to 80 feet of silicified material. Numerous mineralized secfions in excess of 20 feet are indicated on mine maps. Quartz veins that extend into bounding shale units contain low gold values Gold is associated with strong silification and requires fine grinding to liberate. Mineralogy includes, in order of abundance, quartz, feldspar, sericite, chlorite, homblende, mariposite, pyrite, galena, sphalerite, gold, and silver. Base metals are present only in trace amounts. The RGP zone is the westem continuation of the Virgilia zone, which is located at 800 feet lower elevafion. The contrast in elevation indicates mineralization extended over 2000 feet down dip before erosion.
In 1980, Inca Mining Corporation consolidated the land position throughout Rich Gulch and from 19gO through 1984 umdertook an extensive drilling program with the intention of establishing open pit mines at the Virgilia and RGP. A total of 241 drill holes totaling 75,941 feet of drilling were completed. In total, over $5 million was spent on geological, metallurgical, economic analyses, and environmental studies. The program was terminated in mid-1980 with the collapse of the gold price. Inca's published geological reserve for the Virgilia and RGP was 17 million tons ~ 0.084 opt, with mineable reserves totaling 1.5 million tons @ 0.13 opt for the Yirgilia and 3.6 million tons @ O.07 opt for the RGP.
The mining claims were allowed to lapse and the patented claims covering the old Virgilia mine were sold and broken up for home sites. The area of the RGP mine was Federal land amd remained open until 2006 when the present owner covered the property i with lode claims. In 2007, paper records from the Inca drilling program were located. Unfortunately, most of the geologic maps and metallurgical tests, along with pulps and cuttings, had been lost, and reject core, which was stored on the RGP property, was lost in the fire earlier this year. The former Project Manager amd Project Geologist for Inca have been contacted and each has provided valuable information about the drilling program.
California State law forbids open pit mining for metals unless the pit can be refilled and brought back to original condition. This is not practical for the RGP deposit except perhaps for a small area at the west end of the propery. Accordingly, the RGP deposit was examined as an umderground operation, taking advantage of the two large tu~mels which are open (English and Blacksmith) amd several small tunnels which are caved at the portals. The drill hole data were carefully entered into computer databases and evaluated by SURPAC at 100- and 50-foot intervals on strike. All Inca drill hole data was utilized, consisting of 114 holes and 1,647 analytical values, as well as hundreds of underground channel samples from the 1930's which were modeled as individual drill holes.
The RGP deposit was found to consist of 4 parallel 'veins' or silicified zones, all conEtped to a single tuffaceous horizon that pinches and swells and contains thick selvages of slate. The silicified zones dip 65 degrees northeast amd vary from 5 to 70 feet wide. Veins 2 and 3 contain the bulk of the tonnage. The veins are exposed discontinuously at the surface and much of the richer ore is located just below outcrop.
The SURPAC model was limited to volume elements that were bounded by values of 0.05 opt or greater but could include lower values within the. volumes. Values exceeding one ounce per ton were dropped to one ounce. Tonnage was based on 12.5 cubic feet per ton. The figures below should be interpreted as Indicated resources, not Proven.
Table 1 contains the tonnages amd grades from the SURPAC model based on 100 foot vertical sections passed normal to the strike the deposit. The results for each vein are listed separately. Table 2 contains the results for Vein #2 only based on a 50 foot section model. Similar compilations for the 50 foot model for the other veins, and the table of results for the block model, are available upon request.
The difference between the section and block models is based on sample interval and the shape of the seareh ellipsoids used in estimating volumes within the vicinity of sample data. The tonnage estimates for the 2 models will converge with increased sarnple intervals on strike and modeling of the deposit on horizontal slices at constant elevation.
A plan view of the location the drill holes and the 50 and 100 foot sample sections follows Table 2. The sections are numbered -200 through +1800 (feet), beginning at the .1 northwest end of the deposit. The majority of higher grade material is found between Sections O and +650. The figures for Vein 2 in the Section and Block models listed above come from this interval, and the numbers comprising this figure for the section model can be found at the end of Table 2.
A complete set of SIJRPAC cross-sections for the 50-foot section model is provided with the plan view. The polygons for each section were constructed starting from the east end of the deposit. Mineralized intercepts containing a value of 0.05 opt or greater (typically a 5 foot interval from a drill hole) were used to define the boundaries of the polygons. Successive seetions were constructed by advancing 50 feet into the deposit to the west. The new 50-foot volume would usually include additional drill holes and the polygon(s) were redrawn. Each vein contained low grade sections that created gaps in the vein volumes. These low grade sections were not included in the results. The result of the modeling was volume elements defined for each vein from which cubic footage, tonnage, and grade could be calculated for the entire vein or at 50 foot intervals. The values for the 50-foot intervals for Vein #2 are iisted in Table 2.
Underground channel sarnple data compiled on a series of maps in 1930 were included in the model. Individual 5-foot channel samples were modeled as short, horizontal drill holes with a bearing relative to the drill hole grid. Series of cha~mel samples along the walls of a drift were modeled as longer drill holes containing 2 or more samples. The old mine maps did not include a coordinate system or arrow indicating magnetic north.
To correlate the underground samples with the drill hole locations, the map from the i English tunnel was placed over a computer projection of the drilling data and rotated umtil the pattem of the values in the tunnel matched the values of the drill holes at the same elevation. A map containing a plan view of all the underground workings allowed the other mine maps to be oriented relative tothe English Tunnel map. Because the English Tunnel samples could be correlated to the drill hole grid, coordinates could be assigned to the remaining undergroumd samples.
The English Tunnel (Figure 1) is open at the portal but a map dating from 1930. The map shows that a section of the tunnel within the mineralized zone is blocked by a short cave, although this has not been confimmed. The tUnnel follows Veins 2 and 3 for over 600 feet. Two hundred feet above the English Tunnel are the smaller Upper, Middle, amd Trails End Tunnels which are caved at the portals. The Blacksmith Tunnel is 500 feet lower in elevation than tne English Tunnel but was driven on the veins from a point 2000 feet east. This tunnel is open for 1000 feet and could be extended 1000 feet west to provide access to the lower reaches of Veins 2 and 3. Gold values within tbe Blacksmith Tunnel are low but could potentially offset the cost of new turmeling. The various tunnels provide access to parts of the mineralized system over a vertical range of 833 feet.
There is no location at the RGP property that is practical for a cyanide leach operation unless it is fully contained and confined to tanks. A possible altemative would be to ship the ore out of Califomia to Nevada where a leach operation could be established or the ore sold to another mining company. There is an railroad siding 2 miles from the property and the rail line passes near the Nevada border 120 miles east at Hallelujah s Junction. The same rail line passes throUgh Gerlach (Hog Ranch mine) at 159 miles, i Sulfur (Hycroft mine) at 200 miles, and connects to the main Union Pacific line at Winnemucca at 257 miles. Rail rates vary but 8 cents a ton-mile for bulk rock is a reasonable figure.
Lode claims that cover the entire RGP property (12 Federal mining lode claims) are offered for sale with no retained royalty. Sale will include all drill hole data in paper.
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Rich Gulch Project #L700
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