Opal and tourmaline give October an extraordinary range of color, from shifting flashes of rainbow to soft pink and vivid blue-green. Two very different gemstones, one very colorful month.

Markets are weird. Customers are fascinating, my sister is a great saleswoman, the husband is the best sherpa around, friendships abound, and apparently I now own far too many pairs of artisanal alpaca socks.

When you think of sapphires, you probably think blue of that gorgeous, royal sapphire blue. But this November birthstone might have a few surprises up its sleeve, including a whole rainbow of colours and a rather fascinating history.