Brainteaser

Today's brainteaser is a real puzzle. Can any of you Journal readers crack the code?

After some relaxing, the Seekers of Knowledge received a gift from an anonymous person. The gift was a magic scroll case that had 12 gemstones on it. The Seekers were a bit shocked as they knew it was very expensive.
There was a catch with it. They had no idea how to open it. As they looked over the scroll case with amazement, suddenly they heard a voice saying, "The code to open this scroll case is hidden within the stones; you must press each stone in the correct order to open it." The magic faded out.
The stones are in this order on the scroll case: Turquoise, Diamond, Opal, Aquamarine, Topaz, Emerald, Moonstone, Garnet, Sapphire, Amethyst, Ruby, Peridot.

So, what order should the stones be pressed in to open the case?
This is actually not as difficult as it looks, not that is, once the penny drops!