The combined oxide content of all rare earth elements in a deposit, reported as a percentage.
The sum of all rare earth element oxides in a mineral deposit, typically expressed as a grade percentage or parts per million (ppm). TREO is the standard metric for reporting rare earth resource estimates and provides a measure of total rare earth content.
TREO is the headline grade for rare earth projects, and on its own it says very little. Almost all the value sits in four magnet metals — neodymium, praseodymium, dysprosium and terbium — so the split within TREO matters far more than the total.
A high TREO grade dominated by cerium and lanthanum, which are abundant and cheap, can be worth less than a lower TREO grade rich in magnet metals.