Origin story
Shani is the son of Surya and Chhaya, and his stern gaze tests the deeds of every being. He is the lord of Saturn, the great teacher of karma, discipline and patience, and his delays are understood as lessons rather than punishments.
The black colour, the crow, the iron and the blue sapphire belong to Shani. Devotees approach him on Saturdays for relief from suffering and delay, and in Kerala his shrine is often placed beside the Navagraha stones, where oil, sesame and black cloth are offered.
Source: Wikipedia: Shani — https://en.wikipedia.org/wiki/Shani
