mattapinnoite

Mattapinnoite is a rare mineral species, first discovered in 1995 in the Mattaponi River, Virginia, United States. It is named after the Mattaponi River, where it was found. The mineral is a phosphate of lead and tin, with the chemical formula PbSn(PO4). It crystallizes in the monoclinic system and typically forms in the form of small, prismatic crystals.

Mattapinnoite is not a primary mineral, meaning it does not form directly from cooling magma but rather through the alteration of other minerals, in this case, likely through the weathering of tin-bearing minerals. It is found in low-temperature hydrothermal veins and is often associated with other minerals such as pyrite, galena, and sphalerite.

The mineral is of interest to mineral collectors and scientists due to its rarity and unique composition. It is listed in the Mineralogical Association of Canada's List of Minerals and is assigned the IMA status of "valid". However, it is not a recognized mineral by the International Mineralogical Association (IMA), which lists it as a "supergroup" mineral, meaning it is a mineral that has not yet been approved by the IMA but is recognized by other mineralogical organizations.

Mattapinnoite has a hardness of 3.5 to 4 on the Mohs scale and a specific gravity of approximately 6.7. It has a pale yellow to brownish color and a vitreous to resinous luster. Its cleavage is perfect on {010} and good on {100}, and it has a conchoidal fracture.