Slightly bafflingly, there are three birthstones for December. Turquoise, zircon and tanzanite. A conundrum when I am trying to write about each month’s birthstones! I thought about writing about zircon and my mother asked, “Isn’t that the bad guy in Flash Gordon?” I thought about tanzanite and hit another solid wall: I get as far mentally as “It’s purple.” And my brain locks up. Which left me with turquoise, a glorious opaque blue green mineral! In antiquity, turquoise (whic