Bear Lodge

Location: Wyoming, United States (44.494, -104.452 approx.)

Commodities: rare earth elements; thorium

Deposit model: carbonatite · carbonatite deposits

Geology

“In 1991, Hecla reported “total geological reserves for the three main dikes at 4.3 million short tons (3.9 million tonnes) at an average grade of 3.8% total REO” in the first estimate of the Bull Hill deposit, and “roughly 8.5 million short tons (7.7 million tonnes) at an average grade of 3.0% total REO” for the three dike swarms (Wineteer, 1991). The historical resource estimate of 4.3 million short tons (3.9 million tonnes) at 3.8% REO is based on about ten holes drilled in or near the resource area, and it would likely be classified as an inferred mineral resource according to Section 1.2 of National Instrument 43-101.” (Dahlberg and others (2014)) “The Bull Hill deposit consists of an REE-mineralized carbonatite dike swarm and associated enveloping stockwork zones located within and along the western margin of the Bull Hill diatreme. Near-surface iron oxide-manganese oxide-rare earth (FMR) and oxide-carbonate (OxCa) dikes and veins are interpreted to be intensely (FMR) and moderately to weakly (OxCa) oxidized and leached equivalents of the carbonatite dikes at depth. The dike swarm was discovered by Hecla Mining Company and described in an unpublished Hecla report (Wineteer, 1991).” (Dahlberg and others (2014)) “The Whitetail Ridge deposit is located approximately 1,500 feet (460 meters) northwest of the Bull Hill deposit and approximately 500 to 1000 feet (150 to 300 meters) west of the Bull Hill Northwest deposit. The USBM explored a disseminated stockwork REE deposit in the Whitetail Ridge area in the early 1950’s. In 1950, the USBM conducted sampling that identified an REE-anomalous area defined by total REE abundances greater than 2000 ppm. The sampling program was followed in 1951 by a limited drill program that tested the anomalous area with 10 shallow core holes that ranged in depth from 23.5 to 220.1 feet (7 to 67 meters). The drilling identified FMR stockwork veinlets that consist of REE minerals in a matrix of iron and manganese oxides. A re-evaluation of the data by the USBM in 1990 estimated that the area contains about 76.2 million standard tons of material containing 1.5% REO (Gersic et al., 1990). The USBM estimate is considered unreliable and suitable only as an indication of exploration potential.” (Dahlberg and others (2014)) “The 2011 and 2012 drill programs at Whitetail Ridge identified and updated a Whitetail Ridge resource to the Indicated category (2.25 million tons at a grade of 2.61 % TREO). Additional drilling in 2013 resulted in an expansion of the Indicated resource to 4.26 million tons (3.86 million tonnes) at 2.49% TREO; see chapter 14 of this report). Significantly, the Whitetail Ridge deposit is characterized by about a 2.5X enrichment in overall HREE element grade relative to the Bull Hill resource, which adds potential economic upside to the Bear Lodge Project. The deposit remains open, and further drilling is expected to expand the resource and better define the extent of the REE mineralization.” (Dahlberg and others (2014)) The greatest concentration of REE-mineralized bodies occurs in NW-trending dike swarms and stockworks in the Bull Hill resource area. Overall, the REE mineralization extends for more than 1800 meters along the northwesterly trend (Figure 7.3). Individual dikes can reach 80 feet in width (24.4m). (Dahlberg and others (2014))

Published resource estimates

As compiled by USGS USMIN from the cited studies. Resource classes follow the source; "approximate" flags values USMIN reports as approximations. These are not current company reserve statements.

Exploration and site history

• Exploration — 13 drill holes by Duval Corp., 1972–1977 (Dahlberg and others (2014))
• Exploration — 12 drill holes by Molycorp, Inc., 1978–1980 (Dahlberg and others (2014))
• Exploration — Duval Corporation acquired exploration rights and the exploration program identified high-grade occurrences of copper and rare earth metals, and low-grade gold mineralization within an altered syenite-carbonatite alkaline intrusive complex, 1972–1977 (Dahlberg and others (2014))
• Evaluation — Resource estimate: Molycorp first reported resource estimates for rare earth metals on the Bear Lodge property in 1980, 1980 (Dahlberg and others (2014))
• Exploration — Drilling; Hecla Mining; 12 drill holes, 1987–1990 (Dahlberg and others (2014))
• Discovery — Hecla acquired land position; Completes 12 diamond drill holes in several carbonatite dike sets along southwestern flank of Bull Hill; The dike sets are part of current Bull Hill REE deposit, 1986–1991 (Dahlberg and others (2014))
• Exploration — Drilling, 2009–2012 (Dahlberg and others (2014))
• Discovery — The USBM conducted work in the mountains to evaluate REE mineralization in the early 50s, and again in 1990; Sampling identified an REE-anomalous area defined by REE abundances >2000 ppm and drilled (mostly Whitetail Ridge) with 10 shallow cores for REE, 1950–1990 (Dahlberg and others (2014))
• Intermittent Exploration — The USBM conducted work in the mountains to evaluate REE mineralization in the early 50s, and again in 1990; Sampling identified an REE-anomalous area defined by REE abundances >2000 ppm and drilled (mostly Whitetail Ridge) with 10 shallow cores for REE, 1950–1990 (Dahlberg and others (2014))
• Exploration — Drilling, 2010–2012 (Dahlberg and others (2014))

Record imported from USGS USMIN ver. 4.0 (June 2019). Developments after that date appear on facility records, not here; see the methodology.