September
Traditional: Sapphire · Modern (1912 list): Sapphire
Traditional and modern agree here — no 1912 swap for this month.
Birth flower
Aster / Morning Glory
September's traditional birthstone is the sapphire, and it's also the modern stone on the 1912 Jewelers of America list — same stone, no swap. Sapphire is blue corundum, the exact same mineral as ruby just in a different colour, and it's historically linked to royalty and clergy, worn as protection against envy and harm.
The birth flowers for September are the aster, symbolizing love and wisdom, and the morning glory, tied to affection — and, because each bloom lasts only a single day, to a gentle reminder of how brief life is.