Jewellery goes through fads and fashions at auction and something that was out of fashion a few years ago might now be on the up.
Look for strong, bright colours and good transparency.
Antique gems tend to be untreated (modern gems are often heated to ‘improve’ them) which makes them more valuable and antique gems tend to come from premier mines which are now exhausted. Don't just rely on your judgment Just because a jewel may not be to your taste does not mean it is not valuable.
Rhodium plating is a bit like visiting your favorite hair salon. When an electric current is added to the mix, the tiny suspended particles of plating metal bond to the surface of the immersed piece of jewelry. Because of the very bright and shiny nature of rhodium, it gives white gold a nice “pop.”Rhodiumed rings look whiter and brighter. More often than not, white gold pieces of jewelry you see in jewelry stores have been rhodium plated. Again, it gives pieces the “pop” and “zing” that we like and come to expect.
Jewelry plating—including rhodium plating—is essentially covering one metal surface with a very thin layer of another. In this process the item to be plated is dipped in a liquid solution containing the plating metal.
The only way to be absolutely certain is to x-ray the pearls, but a jewellery specialist will have a good idea by looking at the pearls’ shape and lustre. A cultured pearl necklace is worth a few hundred pounds at auction; its natural counterpart comes in at several thousand pounds. Modern diamond cuts are very precise but older cuts are lumpier and less precise.