The Sage Plain Project uranium-vanadium deposits in the Jurassic Salt Wash Member of the Morrison Formation are sandstone-type deposits that fit into the U.S. Department of Energy’s (DOE) classification as defined by Austin and D’Andrea (Mickle and Mathews, 1978) Class 240-sandstone; Subclass 244-nonchannel controlled peneconcordant. Any future deep drilling to explore for deposits in the Permian Cutler Formation would also target this class of deposit. Such deep drilling would penetrate the slightly shallower Triassic basal Chinle Formation (Moss Back Member). Deposit targets in the Chinle would fit the DOE classification as Class 240-sandstone; Subclass 243- channel controlled peneconcordant. These classes are very similar to those of Dahlkamp (1993) Type 4-sandstone; Subtype 4.1- tabular/peneconcordant; Class 4.1.2 (a) VanadiumUranium (Salt Wash type) and Class 4.1.3-basal-channel (Chinle type).

The Sage Plain and nearby Slick Rock and Dry Valley/East Canyon districts uraniumvanadium deposits are a similar type to those elsewhere in the Uravan Mineral Belt. The Uravan Mineral Belt was defined by Fischer and Hilpert (1952) as a curved, elongated area in southwestern Colorado where the uranium-vanadium deposits in the Salt Wash Member of the Morrison Formation generally have closer spacing, larger size, and higher grade than those in adjacent areas and the region as a whole. The location and shape of mineralized deposits are largely controlled by the permeability of the host sandstone. Most mineralization is in trends where Top Rim sandstones are thick, usually 40 feet or greater.

The Sage Plain District appears to be a large channel of Top Rim sandstone which trends northeast-southwest, as one of the major trunk channels that is fanning into distributaries in the southern portion of the Uravan Mineral Belt.

Most of the Uravan Mineral Belt districts consist of oxidized sediments of the Morrison Formation, exhibiting red, hematite-rich rocks. Individual deposits are localized in areas of reduced, gray sandstone and gray or green mudstone (Thamm et al., 1981). The Morrison sediments accumulated as oxidized detritus in the fluvial environment. However, there were isolated environments where reduced conditions existed, such as oxbow lakes and carbon-rich point bars, referred to as carbon facies rocks by Shawe (1976). During early burial and diagenesis, the through-flowing ground water within the large, saturated pile of Salt Wash and Brushy Basin material remained oxidized, thereby transporting uranium in solution. When the uranium-rich waters encountered the zones of trapped reduced waters, the uranium precipitated. Vanadium may have been leached from the detrital iron-titanium mineral grains and subsequently deposited along with or prior to the uranium.

The habits of the deposits in the Sage Plain area have been reported to be typical of the Uravan Mineral Belt deposits. Where the sandstone has thin, flat beds, the mineralization is usually tabular. In the more massive sections, it “rolls” across the bedding, reflecting the mixing interface of the two waters. This accounts for the fact that there are several horizons within the Top Rim that are mineralized. Very thin clay layers on cross beds appear to have retarded ground water flow, which enhanced uranium precipitation. The beds immediately above mineralized horizons sometimes contain abundant carbonized plant material and green or gray clay galls. The mudstone beds adjacent to mineralized sandstones are reduced, but can grade to oxidized within a few feet.

The thickness, the gray color, and pyrite and carbon contents of sandstones, along with gray or green mudstone, were recognized by early workers as significant and still serve as exploration guides. Much of the Top Rim sandstone in the Sage Plain Project area exhibits these favorable features; therefore, portions of the property with only widelyspaced drill holes hold potential. However, without the historic drill data, it cannot be determined where sedimentary facies are located (e.g., channel sandstones thin and pinch-out, or sandstone grades and interfingers into pink and red oxidized sandstone and overbank mudstones). Furthermore, locations of interface zones of the oxidized and reduced environments are hard to predict. Until more historic data are obtained and/or more drilling occurs on the property away from the historic mines, these outlying areas remain exploration targets.

The uranium- and vanadium-bearing minerals in the Salt Wash Member of the Morrison Formation occur as fine-grained coatings on the detrital grains, they fill pore spaces between the sand grains, and they replace some carbonaceous material and detrital quartz and feldspar grains.

The primary uranium mineral is uraninite (pitchblende) (UO2) with minor amounts of coffinite (USiO4OH). Montroseite (VOOH) is the primary vanadium mineral, along with vanadium clays and hydromica. Traces of metallic sulfides occur. In outcrops and shallow oxidized areas of older mines in the surrounding areas, the minerals now exposed are the calcium and potassium uranyl vanadates, tyuyamunite, and carnotite. The remnant deposits in the ribs and pillars of the old mines show a variety of oxidized minerals common in the Uravan Mineral Belt. These brightly-colored minerals result from the moist-air oxidation of the primary minerals. Minerals from several oxidation stages will be seen, including corvusite, rauvite, and pascoite. Undoubtedly, the excess vanadium forms other vanadium oxides depending on the availability of other cations and the pH of the oxidizing environment (Weeks et al., 1959). The Sage and Calliham mines have been standing full of water for at least ten years, so no direct observations have been made of the mine workings. Fragments of ore can be found in the un-reclaimed waste rock pile at the Sage mine. Samples of this material show some of the vanadates mentioned above.

Some stoping areas in the Sage and Calliham mines as well as the nearby Deremo mine to the east and the Silver Bell and Wilson mines to the north are well over 1,400 feet long and several hundred feet wide. The Indicated Mineral Resources of the Sage Plain Project properties identified through drilling are of similar size. Individual mineralized beds vary in thickness from several inches to over 10 feet.

Top Rim sandstone is quite variable because of its depositional nature, but can usually be distinguished by it typically being the first thick sandstone encountered after the Brushy Basin. Across the project area, the individual beds only locally correlate from hole to hole; however, the elevation of the horizon as a whole at which the first thick sandstone bed is intercepted is fairly consistent. The Top Rim consists of sandstone beds, varying widely from multiple 10-30 foot beds to single massive beds 30-70 feet thick. Multiple sandstone beds within the Top Rim are separated by thicker mudstones up to 15 feet thick and the massive beds typically end with thick mudstones, usually signifying the bottom of the Top Rim. Sandstone grain size on average is fine to medium, which is somewhat coarser than in the Uravan Mineral Belt. The thinner multiple sandstone beds of the Top Rim within the project area tend to be very-fine to fine grained.

The mining of all resources in the Sage Plain Project will be by conventional underground methods. These methods have been used very successfully in the region for over 100 years. The nature of the Salt Wash uranium-vanadium deposits require a random room and pillar mining configuration. The deposits have irregular shapes and occur within several close-spaced, flat or slightly dipping horizons. The mineralization often rolls between horizons. The use of rubber-tired equipment allows the miners to follow the ore easily in the slight dips and to ramp up or down to the other horizons. The deposits are accessed from the surface through long declines at gradients of 8-15%, depending on depth and locations suitable for portal sites. The Salt Wash sandstones are usually quite competent rock and require only moderate ground support. The overlying Brushy Basin mudstones are less competent, so the declines are often supported by square set timber or steel arches and timber lagging. The Salt Wash deposits are usually thinner than the mining height needed for personnel and equipment access. Therefore, the ore is mined by a split-shooting method.

The split-shooting mining method involves assessing each face as the stopes advance by the mine geologist, engineer, mine foreman, or experienced lead-miner. Because the grades and thickness of the typical Salt Wash uranium vanadium deposits are highly variable, they are usually unpredictable from one round to the next. (A round is a complete mining cycle of drill-blast-muck-ground support, if needed to be ready to drill again; a normal round advances a face about 6 feet.)

Typically, the thickness of the mineralized material is less than the height needed to advance the stope. As the stope face is being drilled, the blast holes are probed with a Geiger Counter probe in order to estimate the U3O8 grade. The uranium-vanadium mineralization is usually dark gray to black. The mineralization sometimes rolls, pinches or swells, or follows cross-beds within the sandstone. Therefore, the miner will also use drill cutting color as a criterion to help guide blast hole direction and spacing. This irregular habit of the deposit can result in holes collared in mineralized material ending in waste, or, conversely, holes collared in waste can penetrate mineralized material much of their length.

Based on the results of the assessment of the blast holes drilled in the face, the round will be loaded and shot in two or more stages. Depending on the location and thickness of the mineralized material in the face (there may be multiple mineralized layers); the miner will attempt to blast either only mineralized material or only waste rock. They will muck it out as cleanly as possible, then shoot the remaining rock and muck it cleanly. In resource estimates, waste is added to the mineralized material for dilution because of this method for any mineralized zone less than 3 feet thick. The amount of waste rock shot before or after the mineralized material results in typical stope heights of 7 feet, which is the minimum height needed to advance the stope.

As with the split-shooting method of mining, resuing mining involves very selective separation of the waste rock from the ore. Ore grade material is determined by probing drill holes in the face of the stope. In resuing, waste is blasted or otherwise removed from one side of the ore zone. The ore in that zone is then extracted, thereby leaving any waste on the other side of the ore zone in place. If additional stope space is needed or a second ore zone occurs behind the remaining waste, that waste is removed without dilution to the ore zones. The lower limit of waste volume that can be extracted without disturbing ore is a function of the precision with which waste areas of the drill pattern can be selectively blasted without unduly increasing mining costs.

Historically, the uranium-vanadium ores from the Sage Plain District and others districts of the Uravan Mineral Belt have been successfully processed in conventional mills in the region. One mill is currently operational in the region, EFI’s White Mesa Mill at Blanding, Utah, 54 miles away. The milling operation involves grinding the ore into a fine slurry and then leaching it with sulfuric acid to separate the metals from the remaining rock. Uranium and vanadium are then recovered from solution in separate solvent extraction processes. The uranium is precipitated as a U3O8 concentrate, “yellow cake”, which is dried and sealed in 55-gallon steel drums for transport off-site. The vanadium concentrate is precipitated then fused into a V2O5 product called “black flake” which is also transported in 55-gallon steel drums.