Haiweeite is a mineral of uranium and has the chemical formula: Ca[(UO<sub>2</sub>)<sub>2</sub>Si<sub>5</sub>O<sub>12</sub>(OH)<sub>2</sub>]÷3(H<sub>2</sub>O). It is a secondary mineral of uranium, a product of oxidation. It has a greenish yellow color. It has a Mohs hardness of about 3.5 and is fluorescent under UV light.
It was named after the Haiwee Reservoir, Inyo County, California, US, where it was first found.