Kate wore these unidentified earrings to Middle Temple on October 8, 2012.
Here it the closeup:
There is some debate as to whether these are brown or dark red drops. They could be brown, but given that Kate usually coordinates her jewelry to match her outfit, I think it’s likely they could be dark red, perhaps garnet.
They are gemstone drop earrings set in yellow gold. Judging by the way the gold glistens, this could be goldplated brass. I think it’s not solid gold.
Here they are on Kate: