Pink Tourmaline engagement rings? Absolutely! Diamonds may be a girl's best friend, but Pink Tourmaline engagement rings are a unique, original, and a far more affordable choice. Pink tourmaline is a birthstone of October, along with opal, and is a truly special gem. The deep rosy color of a pink tourmaline ring will be sure to attract attention. The birthstone of December, the tranquil azure color of a blue topaz ring can evoke thoughts of warm Caribbean seas on a cold winter day.