olmiite

Olmiite is a rare calcium-manganese silicate that was named after an Italian mineralogist called Filippo Olmi. It was approved by the IMA in 2006, with its first description published in 2007. Around 2001, a large amount of specimens believed to be poldervaartite was discovered at the N'Chwaning II mine, which is near the Wessels mine, where the latter was discovered. Only later were the researchers able to determine through their investigations that the two minerals are different, as they are visually indistinguishable. Until Renato Pagano acquired and examined the specimens, seemingly no specific investigation was carried out. Olmiite has been misidentified not only once, but twice. The cream-colored specimens were at first thought to be baryte by the mine geologist.

== Properties == Olmiite is the Mn2+ dominant analogue of poldervaartite. It typically has a pinkish core color, caused by manganese coloration, and it typically has a colorless outer rim. Olmiite shows a wide variety of crystal habits. It can crystallize in radiating spheres, meaning it grows into an orb-like shape, forming slender crystals which grow from a central point. It can grow as botryoidal, which are hemispherical masses; acicular, which is a needle-like crystal habit; in stacked crystal plates, and wheat sheaf crystal groups. It can also form individual pyramidal crystals, however, those are uncommon. The aggregates are made of minute crystals. Olmiite aggregates on the market typically reach a few centimeters, and an individual crystal can reach up to 7 mm. In nature, specimens can range from thumbnail- to museum-sized slabs covered in olmiite crystals. However, most of the minerals only occur as tiny grains in rocks, which have to be found using a microscope. Olmiite mainly consists of oxygen (39.32%), manganese (22.95%) and calcium (22.65%), but otherwise contains silicon (13.81%), and has a negligible amount of hydrogen (0.99%) and iron (0.27%) in its formula as well. It shows no signs of radioactivity.