That bangle was shot about seven months ago. If I remember correctly, it was a set of two and together the price tag was in the neighborhood of $17,000. They were estate pieces from the Victorian period.
It might have been possible to have shot two separate images of the brooch and then blend them, but that would have required two lighting setups. Remember, those two were shot on a 4x5 view camera with a studio light. The difference between working with a 4x5 view camera and a DSLR is like the difference between getting a donkey and a terrier to jump through a hoop.
In digital photography, the most common solution for presenting diamonds as perfectly lit stones which reside on the same plane is to clone one diamond (or two if the tops of the diamond reside on two planes) and then drop it into the setting. This is more commonly done in generic representations ("here 's a diamond ring") rather in specific representations of jewelry for sale ("this diamond ring costs $50,000"). If you look at enough jewelry advertisements (especially the ones in the jewelry trade magazines) you'll notice that this is common. You won't see it done in specific pieces for sale very often, though (if ever).