hewettite

Hewettite is a rare, naturally occurring mineral composed of calcium vanadates. Its chemical formula is generally represented as CaV4O9·n H2O, though the exact hydration state can vary. It is known for its vibrant yellow to orange-red color. Hewettite is often found in arid environments, particularly in association with other vanadium-bearing minerals.

This mineral was first discovered in the Callao Mines in the Cerro de Pasco Region of Peru. It was named in honor of Don B. Hewett, a geologist who extensively studied the vanadium deposits in Peru. Hewettite typically forms as small, granular aggregates or coatings on other rocks. It can also occur as acicular or prismatic crystals, though these are less common.

Hewettite is a secondary mineral, meaning it forms from the alteration of pre-existing minerals. It is often found alongside minerals like vanadinite, descloizite, and carnotite. Due to its rarity and vibrant color, hewettite is of interest to mineral collectors. It is not a significant ore of vanadium, as other minerals are more economically viable sources. Its primary occurrence is in oxidized zones of vanadium-bearing deposits.