Rhabdophane

Rhabdophane is a phosphate mineral with the chemical formula (REE)PO4·H2O, where REE represents a mixture of rare-earth elements. It is the hydrated phosphate mineral of rare-earth elements. The mineral is typically found in pegmatites, metamorphic rocks, and sedimentary rocks. It can also occur in hydrothermal veins and as a detrital mineral in sands and clays.

Rhabdophane commonly exhibits a pale yellow to brown color. It crystallizes in the hexagonal crystal system and typically forms as small, irregular prismatic crystals or as granular masses. It is relatively soft, with a Mohs hardness of 3.5 to 4, and has a vitreous luster. Its density is around 3.6 to 3.8 g/cm³.

The rare-earth elements found in rhabdophane include lanthanum, cerium, neodymium, and praseodymium. Cerium is often the most abundant rare-earth element in rhabdophane, leading to the variety named 'cerorhabdophane'.

Rhabdophane is not a major ore of rare-earth elements, as deposits are often small and dispersed. However, it can be an indicator mineral for the presence of rare-earth mineralization in certain geological settings. Its presence can also be studied to understand the geological conditions under which rare-earth elements are mobilized and deposited.