How many letters does the top answer for “a native hydrated silicate of alumina, lime, and potash, first noticed near rome.” have?

The most common answer is gismondine (10 letters).

Crossword clue: a native hydrated silicate of alumina, lime, and potash, first noticed near rome.

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

gismondine 10 letters web-def

A native hydrated silicate of alumina, lime, and potash, first noticed near Rome.

gismondite 10 letters web-def

A native hydrated silicate of alumina, lime, and potash, first noticed near Rome.