Penfieldite is a mineral that belongs to the carbonate group, more specifically to the calcite group. It has a chemical formula of CaZn(PO4)2·2H2O, indicating a composition of calcium, zinc, phosphorus, and water molecules. Named after the renowned American mineralogist Richard Penfield, penfieldite typically occurs as fine-grained, radiating masses of crystals, often exhibiting a silky or fibrous texture.
This mineral usually forms in the oxidized parts of zinc ore deposits, commonly associated with other phosphate minerals such as wavellite and tarbuttite. It is most commonly found in regions with high concentrations of zinc, like the Franklin Mine in New Jersey, United States, and the Nakauri mine in Hyogo, Japan.
Penfieldite exhibits a pale yellow to greenish-yellow color with a pearly to vitreous luster. It has a monoclinic crystal structure and a Mohs hardness of 4, which means it can be easily scratched by harder minerals. When subjected to ultraviolet light, penfieldite may emit a weak bluish-white fluorescence.
Although penfieldite is not widely used commercially, it holds significance in the field of mineralogy due to its unique crystal structure and formation conditions. Its identification in geological samples can help geologists and mineralogists understand the conditions under which zinc ore deposits form and provide valuable insights into the geological history of a given area.
