What is "siderotype"

Siderotype is an iron-based photographic print. The term was coined by Sir John Frederick William Herschel. A short list of processes defined as siderotypes is as follows: amphitype, argentotype, argyrotype, aurotype, breath print, Brown Line, chromatic photo, chrysotype, cyanotype, ferrogallic process, kallitype, kelaenotype, Nakahara's process, palladiotype, pellet print, Phipson's process, platinotype, printout platinum, satista print, sepia platinotype, sepiatype and vandyke.