Crossword clue: an opaque form of quartz; red or yellow or brown or dark green in color; used for ornamentation or as a gemstone

The most common answer is jasper (6 letters).

1 answer found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

Possible answers

jasper 6 letters wn-def

an opaque form of quartz; red or yellow or brown or dark green in color; used for ornamentation or as a gemstone