Spotting synthetics in Art Deco pieces?

[Circe]

I don't know if this should go in Colored Stones or Jewelry Pieces, but either way, I figure I'll get expert advice!

I love vintage pieces, and I'm especially drawn to Art Deco these days - the clean geometry and the bright contrasting colors really appeal to me. A lot of those pieces use synthetic sapphires, rubies, and emeralds (the development of synthetics was eagerly embraced by Art Deco jewelers, who were delighted to find a source of bright, clean stones for their designs - the origins weren't considered "lesser," or even particularly important, insofar as I'm aware). When I find a gorgeous vintage piece, I'm not too concerned either, but I'm just curious: any immediate tells for whether those gorgeous tiny baguettes are true or false? Wear patterns, tell-tale zoning, anything?

 

[chrono]

With synthetics, one usually does not get colour zoning. Not foolproof but a synthetic stone is always extremely clean whereas a natural stone usually has some inclusion or two when magnified. Unless you are able to spot natural growth lines, that’s another sign of a natural sapphire.

 

[Treenbean]

Ruby
As is the case with emerald, it's important to know how to identify natural from synthetic ruby because of the dollars at stake. The extraordinary thing about synthetic rubies is that you are bound to find one or more in original art deco jewelry. The creation of a synthetic gem was a technical marvel back then, not a way to achieve more affordable gems. To match 30 or 40 “Burma” color rubies, synthetics were commonly combined with naturals. Gas bubbles and curved striae will be obvious in synthetic rubies found in art deco pieces. Created rubies from later in the 20th century have more subtle gas bubbles and striae.

Flux rubies were created in the latter half of the century. They show white “fluxy” fingerprints and platinum triangular platelets, similar to those seen in other flux-created gems. Platinum is less apparent in the newer product. In Ramaura synthetic ruby, the created ruby begins its growth suspended in the melt instead of starting from a “seed crystal” at the bottom of the crucible. The resulting ruby shows fewer flux inclusions but some unusual angular graining. It is very difficult to make identifications based solely on wavy angular graining patterns. That's why, when identifying the Ramauras and the latest hydrothermal synthetic rubies, you must be absolutely sure before you make the call.

Curved striae are highly characteristic of synthetic rubies grown by the flame-fusion process. Deposits of successive flow layers create the pattern we associate with this synthetic. 15x.

Both primary and secondary flux inclusions are visible in this flux-grown synthetic ruby. Such inclusions are generally considered to be proof of synthesis in rubies. The heat treatment of natural rubies, however, can create some similar internal patterns, thereby clouding the issue. 20x.

More info http://www.jckonline.com/article/283964-Synthetics_in_Your_Inventory_Here_s_How_to_Tell.php