Paleozoic sedimentary rocks of northern Arizona are host to thousands of breccia pipes. Rocks cut by these pipes range in age from the Mississippian Redwall Limestone through to the younger Triassic Chinle Formation. These rocks encompass about 4,000 ft (1,200 m) of stratigraphic section of erosion yet no single pipe has been observed that cuts through the entire section as erosion and other factors come into play. No pipe is known to occur above the Chinle Formation or below the Redwall Limestone.

Breccia pipes within the Arizona Strip are near vertical, circular to elliptical bodies of broken rock. This broken rock is composed of slabs, fragments and rotated angular blocks of the surrounding and/or stratigraphically higher formations. Many geologists consider the pipes to have been formed by solution collapse of the underlying carbonate rocks (such as the Redwall Limestone). The blocks and slabs are set in a matrix of finer-grained material from the surrounding and overlying rock formations. In most instances, the matrix has been cemented by silicification and calcification.

Breccia pipes consist of three interrelated features: a basinal or structurally shallow depression at surface; a breccia pipe underlying the structural depression; and annular fracture rings around the margins of the pipes. Annular fracture rings are commonly, but not always, mineralized. The structural depression may have diameters greater than 0.5 mi. (800 m), whereas the breccia pipe diameters typically range from 200 ft (60 m) to 300 ft (90 m), up to 600 ft (180 m).

Mineralized breccia pipes discovered to date often occur in clusters or trends. Spacing between pipes ranges from some hundreds of feet within a cluster to several miles within a trend. Pipe location may have been controlled by deep-seated faults but karstification of the Redwall Limestone in Mississippian and Permian times is considered to have been a key control of breccia pipe formation in the region.

Uranium mineralization in the breccia pipe deposits occurs largely as blebs, streaks, small veins and fine disseminations of uraninite-pitchblende (UO2). Mineralization is generally confined to the matrix material, but it may also extend into the breccia fragments, particularly where these fragments are of Coconino sandstone. An extensive suite of anomalous elements has also been reported, including: silver, arsenic, barium, cadmium, cobalt, chromium, cesium, copper, mercury, molybdenum, nickel, lead, antimony, selenium, strontium, vanadium and zinc (Wenrich, 1985). In addition, many of the rare earth elements are consistently enriched in uranium mineralized samples. Within some pipes copper occurs in sufficient concentrations to be economic whereas significant gold is only known in the Copper Mountain mine. Silver is almost always anomalously high and some of the pipes carry potentially economic grades.

Within many pipes, there is a mineralogical zonation in and around the uranium mineralization.

Uranium mineralization within EZ1 occurs at two distinct vertical intervals, referred to here as the Upper zone and the Lower zone. The Upper zone is contained within a vertical interval of approximately 400 ft (120 m) between the elevations of 4,026 ft and 3,636 ft (1,227 m to 1,105 m). The elevations correspond to depths below surface of 1,170 ft and 1,560 ft (357 m and 475 m), respectively. At its widest point, the Upper zone has a diameter of 183 ft (55.5 m). The Lower zone occurs between the elevations of 3,373 ft and 3,042 ft (1,028 m to 927 m) and covers an interval of 331 ft (101 m). The elevations correspond to depths below surface of 1,812 ft (552 m) and 2,143 ft (653 m), respectively. At its widest point, the Lower zone has a diameter of 45 ft (13.7 m).

The geometry of the Upper zone is controlled by the regional structure. Initially, it plunges to the southeast at about -57o along an azimuth of 135o until it reaches a depth of 1,400 ft (427 m). At this point it changes to a vertical attitude down to a depth of 1,560 ft (475 m). Because there are no barren drill holes to the southeast of the Upper zone, there is the potential for additional drill intersections to the southeast (in plan view) along an azimuth of ~135o.

The geometry of the Lower zone appears to reflect the increased porosity of the Esplanade Sandstone and consists of a narrow vertical plug occupying the lower throat of the breccia pipe. This plug has an average width of 37 ft (11.3 m).

Uranium mineralization at EZ2 occurs at three distinct zones: an Upper zone, a Lower zone and a diffuse, Middle zone, half way between the Upper and Lower. The Upper zone consists of a large, mostly stratiform deposit, located primarily within the Coconino Sandstone. A single satellite deposit is also included in the Upper zone. The larger Upper zone is mushroom-like in shape and occurs between the elevations 4,169 ft (1,271 m) and 3,185 ft (971 m). It has a maximum width (in plan view) of 303 ft (92 m) when measured parallel to the longer axis of the zone; the shorter dimension is 269 ft (82 m). The pipe-like part of the Upper zone averages 57 ft (17.4 m) in diameter.

The Middle zone is made up of two central deposits surrounded by multiple “ring” deposits. One of the deposits within the ring has a much greater volume when compared to the other nine satellite bodies and it may represent potentially significant mineralization in the ring fracture system. This entire array of deposits occurs between the elevations 3,954 ft and 3,781 ft (1,205 m and 1,152 m) and appears to be encompassed by a ring fracture system that is 350 ft (107 m) in diameter. This size is not atypical for breccia pipes of this region.

The Lower zone consists of a central deposit occupying the throat of the pipe and one small, fracture-associated satellite ore body. The central ore body (in this Lower zone) occurs between the elevations 3,722 ft and 3,624 ft (1,134 m and 1,104 m) and also takes the form of a mushroom-like structure. The long dimension of the zone is 161 ft (49 m) and 140 ft (42.7 m) along its minor axis. The average diameter of the pipe-like structure at the base of the Lower zone is 68 ft (20.7 m).

The satellite deposit in the Lower zone is represented by an arcuate solid approximately 20 ft (6 m) long and 10 ft (3 m) tall with a thickness in plan view of 7 ft (2.1 m).

The conceptual mine plan for the EZ1 and EZ2 Complex is based on accessing the two pipes from a single shaft located between them. The pipes will be reached by horizontal tunnels at or below the lower reaches of the mineralized sections. The common surface facility will be the main shaft, working space for waste piles, stockpiles, water impoundments, and all buildings and related infrastructure.

The use of a single shaft will provide more rapid access to a large volume of potentially economic mineralization and will also reduce the overall capital development expenditures when compared with the development of two shafts. Utilizing a single shaft and three ventilation shafts will minimize the surface impacts. This will be more favourable for permitting considerations.

By developing both breccia pipes simultaneously, multiple working areas will be available which will allow increased operational flexibility and sustainable production. All potentially economic mineralization will be hoisted up the main shaft where it will be loaded into haulage trucks and transported to the White Mesa mill in secured, over-theroad trucks. The haulage distance from the EZ1 and EZ2 pipes to the White Mesa mill is approximately 310 miles.

Mining will employ the same methods currently in use at Energy Fuels’ active and planned breccia pipes. It is anticipated that the bulk of the mineralization will be extracted using blasthole slot mining.

Processing of any mineralized material from either breccia pipe is expected to take place at Energy Fuels’ White Mesa mill near Blanding, Utah. The basic mill process is a sulphuric acid leach with solvent extraction recovery of uranium and vanadium. In general, the mill operates on a campaign basis in order to stockpile sufficient material for processing.