Mineral/rock

Derived from or for

Ramsdellite

Lewis Stephen Ramsdell (1895-1975), American mineralogist, U of Michigan, Ann Arbor

Rare earths

named by Johann Gadolin as a literal description of a group of elements

Rhodochrosite

Greek rhodochros = rose colored alluding to its color

Rhodonite

Greek rhodon = a rose alluding to its color

Roseki

Japanese for waxy stone referring to its wax-like appearance. 

Roscoelite

Henry Enfield Roscoe (1833-1915), a chemist from Manchester, England, who first to prepared pure vanadium

Ruby

Latin rubeus = red alluding to its color

Rutile

French shining from Latin rutilus = red alluding to its color