Didymium and its rare earth oxides are used to color glass. The glass is important for blacksmithing and glassblowing safety glasses. Unlike dark welder glasses, didymium glass selectively filters out yellow light, around 589 nm, reducing the risk of Glassblower's cataract and other damage while preserving visibility.

Didymium is not a name you will often find in textbooks these days. It is the name of a pair of elements which lie next to each other in the lanthanide or rare earth series - what used to be the Wild West of the periodic table. The fourteen elements that constitute the series are remarkable for their similarity.

The actual ratio of neodymium to praseodymium varies somewhat depending on the source of the mineral, but it is often around 3∶1. Neodymium is always present in higher proportions than praseodymium and is responsible for most of the color of didymium salts.

Didymium Oxide is a mixture of Neodymium Oxide and Praesodymium Oxide used in optical glass. Dydium glass filters are ideal wavelength reference materials in the high end visible/near NIR region. Dydmium oxide is generally immediately available in most volumes, including bulk quantities.