I would get more information on it; Who found it, Where was it found? , And, as you are trying to find out, is it real.
My feeling is that it looks iffy, without any provenance.
I think it could be authentic. Would have to see it in person. It's made from the correct material for a hardstone pendant at least. Would love to see it sometime.Hippy
Like Hippy said, I wouldn't comment on authenticity without seeing it in person. Porphyry was a highly prized material in our area and if it is a good one, its a really good one!
Jonzer - I don't see anything about the piece that is significantly problematic for me. I'm sure holding in hand you have a substantially better feel on it's authenticity than we can. Out of curiosity, what is your opinion on the piece?