psephite
/ˈ(p)sɛfʌɪt/Geology
noun
A coarse-grained breccia, conglomerate, or similar sedimentary rock; (in later use) specifically such a rock after metamorphic alteration.
Origin
Early 19th century; earliest use found in Henry Thomas De la Beche (1796–1855), geologist. From ancient Greek ψῆϕος pebble, round stone + -ite, after French psêfite.