Crossword clue: a trivalent metalloid element; occurs both in a hard black crystal and in the form of a yellow or brown powder

The most common answer is boron (5 letters).

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

Possible answers

boron 5 letters wn-def

a trivalent metalloid element; occurs both in a hard black crystal and in the form of a yellow or brown powder