CREATE TABLE table_203_613 (id DECIMAL, "formula" TEXT, "color" TEXT, "symmetry" TEXT, "space group" TEXT, "no" DECIMAL, "pearson symbol" TEXT, "a  ( pm ) " DECIMAL, "b  ( pm ) " DECIMAL, "c  ( pm ) " DECIMAL, "z" DECIMAL, "density ,  g/cm3" DECIMAL)

which formula has a density , g/cm3 of at least 15 ?
SELECT "formula" FROM table_203_613 WHERE "density, g/cm3" >= 15
SELECT "formula" FROM "table_203_613" WHERE "density, g/cm3" >= 15