I am looking for an engagement ring for my would-be son-in-law, and both my husband and I are quite perplexed about the right kind of gem for his gold engagement ring. Can somebody please advice between blue sapphire, turquoise, and emerald, which would make a durable and practical engagement ring for him to wear every day? Moreover, would there be any affect of gemstones to his personality and health! He is a Sagittarian, and we would like to present a perfect gold engagement ring, which should be lucky for him. Please suggest!