Discovered : by F. Reich and H. Richter in 1863 Isolated in Frieberg, Germany Origin : The element is named after indigo, which is the colour of the brightest line in its spectrum. Description : A soft, silvery metal that is stable and used in low-melting alloys for fire-sprinkler systems in shops and warehouses. Some semi-conductors and transistors are made of indium arsenic and indium antimony. Image : Japanese symbol 'hon', meaning origin.