No way. I have bought a few diamonds in my 55 years and learned a long time ago to never buy diamonds or really any kind of jewelry from a jewelry store or any kind of store for that matter. They sell low grade diamonds with 400% markup.
Just about every city has a Diamond Exchange. There you will find the good diamonds that have certification grade, color and flaws and engraved with a laser. Last time i went I bought my wife 1 carrot diamond for our 25th anniversary last year, the diamond cost round $890, and set into a 18 K gold ring totaled around $1200. Took it to have it appraised and it tipped in at $5250 which is just what it would about sell for at a jewelry store.
As far as your replacement diamond, if it is not a quality investment grade diamond take it to a jewelry store that does in house repairs and/or makes jewelry, NOT SEND THEM OFF somewhere else. So no do not buy anything that is suppose to be valuable on an island. 99% of the time it is counterfeit or just plain junk. Stick with Tee-Shirts and tutti-fruitti drinks with umbrella stir sticks. :doubleup: