Is a birthstone or any gemstone for that matter kosher for a man to wear (e.g: around the neck) according to the Rabbis or is it prohibited as 'You shall not wear a woman's garment as that is a degredation' (Devarim 22:5)?
Note the connection between the gemstones and Ahaarons haKohen Gadols breastplate (if there is any, according to the wikipedia article Josephys is said to mention that alleged connection).