The Needles and Capitan Deposits are bedded or sedimentary magnesite deposits. Needles is the better exposed of the two, with magnesite mineralization occurring in a shallow basin as a thin lens estimated to be 600 feet wide and 2,400 feet long with a maximum thickness of 12 feet.
The Vitaliano Report (1950) showed magnesium (MgO) grades as high as 46.3% (relative to the maximum theoretical grade of 47.8%) with 117,000 mt of “indicated ore” and 410,000 mt of “inferred ore” over a project area of 123,600 m2 at the Needles Deposit.
The California Geological Society classified the Needles Deposit as unusually pure and over 500,000 mt of magnesite ore exposed at the surface, with additional resources expected at depth.
The Kraemer Report (2020) updated this work and estimated the Needles Deposit project area could extend up to 480,000 m2, potentially containing up to 2 million tonnes of magnesite.
The SWCA Reports (2020-2022) outlined an initial 500,000 mt deposit, 10-year mine life, and 20,000 mt annual production of magnesite ore.
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