SLATIEST
Scrabble letter values: S1L1A1T1I1E1S1T1 = 8
Definition
SLATIEST is the superlative of SLATY.
adjective SLATY: of the color of slate or granite.
Synonyms of SLATY: slate-grey, slate-gray, slaty-grey, slaty-gray, slatey, stone-grey, stone-gray