The USGS describes this as "Potentially the Largest Global Resources of Niobium & Rare-Earth Elements"
See related article: http://miningmarketwatch.net/QRE.htm 
 

News today of Quantum Rare Earth Developments Corp. (TSX-V: QRE) (Frankfurt: BR3) (US Listing: QREDF) acquiring the Elk Creek carbonatite is considered an industry coup and propels QRE.V to the fore of the mining sector for both REE and niobium exploration and development. The Elk Creek carbonatite, measuring ~7 square kilometers in southeastern Nebraska, is acknowledged by the USGS as 'potentially the largest global resources of niobium and rare-earth elements' and was successfully targeted in the past by Molycorp in the 70s and 80s (before its parent entity Unocal ran into financial trouble and China forced the closure of REE development in North America). QRE.V will own 100% of the project via acquisition of Nebraska registered Elk Creek Resources (as a wholly owned subsidiary) which has essentially purchased 99% of the core area plus additional fringe portions employing the same land assembly process that Molycorp had used; via options on both surface and mineral rights. Molycorp had put in a total of 105 drill holes and outlined several different deposits at Elk Creek some of which are rare earth and some of which are niobium (a steel hardener with superior qualities than molybdenum).
 

Targeting Largest Global Resource of Niobium: Historic (non NI 43-101 compliant) results on the Elk Creek Carbonatite from 105 drill holes performed by Molycorp revealed 39.4M tonnes of 0.82% niobium with the deposit open to the North, West and at depth. To put this in perspective, currently the Niobec mine of IAMGOLD is the only mine in North America that produces niobium; Mining MarketWatch Journal research indicates IAMGOLD generates net income of ~$100M+ per annum from Niobec which currently has a reserve figure of ~32M tonnes of 0.56% niobium -- comparatively QRE.V now appears to have a company-maker in niobium alone.
 

Targeting Largest Global Resource of Rare-Earth Elements: Within the massive carbonatite there are several recorded occurrences of rare earth elements. Molycorp did not put in enough drill holes to calculate a resource for REEs however their geologists used terms to describe the situation unfolding in terms of 'tens of millions and megatonnes'. Drill hole intercepts (non NI 43-101) included 608ft of 1.18% lanthanides, 630 ft of 1.3%, 110ft of 2.09%, 460ft of 2.19%, 60ft of 3.89% -- Mining MarketWatch Journal notes these figures are massive and very good grades.