Zellerite

Zellerite is a dimorph of meyrowitzite. It is a uranyl carbonate.^[2] It is an acicular mineral, and occurs in crystals that resemble the shape of needles.^[3] It can occur as fine hairlike fibers as well. The size of each crystal is up to 2 mm, and it grows in roughly radial aggregates, veinlets, and incrustations. Elongation is possible.^[4] It has pleochroic attributes, which is an optical phenomenon. Depending on which axis the specimen is being inspected, it can occur as it changes color. Upon being inspected on the x or y axis, the mineral can seem to be colorless, but on the z axis, it is seen in a pale yellow color. The mineral also shows luminescence. Under both a short wave and a long wave ultraviolet light, it fluoresces in green patches.,^[2] which is typical for Uranium compounds. The fully hydrated form of the mineral is lemon yellow, but in transmitted light, it has a very pale yellow color. The dehydrated version of the mineral is called metazellerite.

Zellerite is also radioactive: the concentration of the mineral per Gamma Ray American Petroleum Institute Units is 280.20, due to it consisting of 45.76% uranium. The remaining constituents are oxygen (39.98%), calcium (7.70%), carbon (4.62%) and hydrogen (1.94%).^[3] This rare mineral forms in the weathering zone as an oxidation product of uraninite-coffinite, in the presence of an oxidizing pyrite, where the pH is greater than 7 and the partial pressure of carbon dioxide is greater than the atmosphere's. It is associated with metazellerite, gypsum, uranophane, meta-autunite, schoepite, iron sulfides, limonite and opal.^[4]