This is what CHAT GPT says
The cutoff values in parts per million (ppm) for Light Rare Earth Elements (LREE) and Heavy Rare Earth Elements (HREE) vary based on the specific mineral deposit, the market demand, and the economic feasibility of extraction. However, typical cutoff values can be provided for general understanding:
1. **Light Rare Earth Elements (LREE)**: LREEs include elements like lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), and europium (Eu). For many LREE deposits, a cutoff grade might range from about 1,000 to 2,000 ppm (0.1% to 0.2%).
2. **Heavy Rare Earth Elements (HREE)**: HREEs include elements like gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), as well as yttrium (Y). Because HREEs are less abundant and generally more valuable, cutoff grades for HREE deposits are often lower, typically ranging from 200 to 500 ppm (0.02% to 0.05%).
These cutoff values can vary widely depending on factors such as the type of deposit, the distribution of rare earth elements within the deposit, the presence of other economically valuable minerals, extraction and processing costs, and current market prices.
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