What is another word for "inflexible"?

Roget's Thesaurus (1911) lists these synonyms for "inflexible": absence, adamant, adamantean, adamantine, and, are, arms, block, board, bone, bony, brick, buckram, calculous, callosity, cartilage, cartilaginous, cast, cement, concrete, corneous, crag, crystal, crystallization, deal, durity, elasticity, faith, firm, flint, fort, fossil, gens, granite, granitic, gritty, hard, harden, hardness, hardware.