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The rare-earth elements are the 15 lanthanide-series elements, including lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. Yttrium and scandium, although not lanthanides, are generally included with the REEs, as they often occur with the lanthanides and have similar chemical properties.
Rare Element Resources' Bear Lodge, Wyoming property contains the "light" REEs (lanthanum, cerium, praseodymium, neodymium, samarium, europium, and gadolinium). Four of these, cerium, lanthanum, neodymium, and praseodymium, listed in decreasing abundance, make up the majority of the Bear Lodge distribution, and neodymium and praseodymium are especially valuable. The Bear Lodge rare-earths are concentrated in carbonatite dikes, primarily at an area named Bull Hill, near the center of the large alkaline intrusive complex. Carbonatite bodies range in size from veinlets to dikes and approach 15 meters in width. A swarm of wide carbonatite dikes, striking northwesterly and dipping steeply to the southwest, are located beneath the southwest slope of Bull Hill. The minerals containing rare-earths within the carbonatites are mainly ancylite and bastnaesite. Drill holes penetrating Bull Hill have encountered a swarm of several closely spaced dikes and one main thick dike ranging up to 15 meters in true thickness. The dike swarm has been traced up to 300 meters along strike, and the dikes are open along strike and down dip.
Hecla Mining Company explored the Bear Lodge rare-earth mineralization in the late 1980s, focusing on a swarm of three carbonatite dikes at Bull Hill. Hecla drilled 12 core holes into the system, intercepting multiple rare-earth concentrations in nearly every hole; earlier, four holes drilled by Duval and Molycorp also had intercepted rare earths. Based on the 16 holes with rareearth intercepts completed by 1991, Hecla estimated the rare-earth-element resource to be approximately 3.9 million metric tonnes (4.3 million short tons) averaging 3.8% total rare-earth oxides. **
Rare Element Resources has continued exploring the Bull Hill carbonatite dikes with three core drill holes in 2004, two core holes in 2005, and three core holes in 2007, all encountering varying quantities of carbonatite dikes and rare-earth occurrences. The historical grades and thicknesses of rare-earth-bearing carbonatite have been verified by Rare Element Resources' recent drilling programs. Metallurgical test work has been conducted at several laboratories and a new metallurgical testing program is ongoing using samples from the 2007 drilling. One of Rare Element Resources' goals, building on the recent exploration success, is to estimate an N.I. 43-101-compliant resource of the rare-earth elements deposits.
** These data are historical and were prepared before the introduction of National Instrument 43-101- Standards of Disclosure for Mineral Projects ("NI 43-101"). They may not be relied upon until they are confirmed using methods and standards that comply with those required by NI 43-101. Investors are cautioned that a qualified person has not completed sufficient work to classify the historical estimate as a current mineral resource. Neither the Company nor its personnel treat these data as defining a current mineral resource as defined under NI 43-101, nor do they rely upon them for evaluation purposes; however, these data are used to guide exploration as the Company develops data to support a current mineral-resource estimate in accordance with the requirements of NI 43-101.