Peruvian opals change color

There was a discussion recently about Peruvian Opals which reminded
me of a few strands I purchased back about 5 years. The stones I
used for pieces-earrings, necklace, etc., have maintained their clear
sea blue colour, but… the strands I put away & another large
pendant piece are either turning green around the edges, turning
completely green or losing their colour entirely & speckled with
white spots.

These were not cheap strands & I bought them from the dealer I’ve
been buying stones from for years. The heavy matrixed PO’s have
maintained their colour, as have the opaque dark blue ones.

My question is this: Can Peruvian opals change colour? How can I be
sure these ARE Peruvian opals? If I’m selling a piece to someone &
claiming Peruvian opals, they NEED to be Peruvian opals & not change
color on the wearer. & if they’re not PO’s, how do I approach my
dealer about this? There’s a whole trust issue involved. My
knowledge of stones is limited & though I can look at most coloured
gemstones & know what they are, I’m counting on the dealer. Also,
Larimar seems to be the new “Peruvian opal”. Why is it so expensive &
what makes it so desirable?

Thank you for your help,
Cristine McC

Sounds like they’ve been dyed or plastic filled. However, the
discoloration might also be caused by an acidic reaction from natural
skin oils and perspiration reacting with the hydrated copper material
responsible for the color in the first place.

Wayne Emery
The Gemcutter