How many letters does the top answer for “a white mineral consisting of magnesium carbonate; a source of magnesium” have?

The most common answer is magnesite (9 letters).

Crossword clue: a white mineral consisting of magnesium carbonate; a source of magnesium

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

magnesite 9 letters wn-def

a white mineral consisting of magnesium carbonate; a source of magnesium