I don't have a chalcedony set yet, as I currently want a happy, bright color stone (e.g. my request for a blue agate set).
I wear a lot of stripes in the summer, and the one time I tried it on a 20, it looked too mellow against my happy stripes!
I think chalcedony looks gorgeous against black, and I wear tons of black in the winter. I used to wear black all the time, 24x7, day & night, work & play, so I'm trying to get away from so much black.

Black looks great with colored stones & gemstones for sure!
For me, jewelry is not so much about my skintone vs. working with my outfits. The Oscars recently had tons of nice bling, and no one looked bad. I've never seen high jewelry look bad on anyone as the jewelry stands on its own. Everyone had outfits and jewelry that coordinated well; either by complementing the dress and jewelry or contrasting.
I see more of how the individual piece looks. In this view, I think chalcedony only looks good in WG. It's cool and dreamy. It would not be the same in YG or RG. If you like chalcedony, I think chalcedony would look amazing with the right outfit and clothing colors. It's a beautiful stone.
That was cute about duty-free shopping... I know exactly what you mean.
Speaking of duty-free.. I'm headed off to London later today... I haven't been there since Nov 2019, pre-COVID and pre-Brexit. I think duty-free at LHR is over. I am not one to buy branded jewelry overseas as I prefer to buy it in the US. However I am fine with buying clothing & shoes that I know I will not need altered. There is a Chanel boutique at T3 that always seems to have shoes in my size 38. Believe it or not, that's one of the highlights at the end of my trip, to see what last minute surprise shows up. It's gotten so fun, it's a ritual for me now. I even stay at the LHR Marriott the night before so I can hit the boutique in the morning when they open, before I board.

I am sure you have done wild things like that too!