👉 Ullmannite is a mineral that is composed of quartz, iron oxide, and aluminum oxide. It is named after the physicist Robert Ulrich von Ullmann who first described it in 1920. Ullmannite has a very specific chemical composition and is known for its unique optical properties. Its color changes from orange to yellow at different wavelengths of light, indicating that it absorbs or reflects certain colors differently than other minerals. This property allows it to be used as an optical
