Tips on What to Look For On A Star Sapphire
1. First thing to look at is the bottom, if there is an "L" stamped in the stone, it's a Linde Star and synthetic... Linde stars were manufactured en masse by the Linde division of Union Carbide since about the early 1950â€™s.
2. Next look for imperfections within the stone, or an unevenness on the bottom, or stripes or bands of color that shows through the top, most naturals have one or more of these natural imperfections.
3. Take a good look at the star itself, using a flashlight, most natural stars do not have a "perfect" star, whereas the natural will likely have one or more of the six legs uneven in length, or maybe not perfectly straight... the star must travel around following the light source, if the star is stationary it is definitely synthetic. The most common synthetics jump out as way are too perfect looking and the star might only move one direction if at all.
4. Color is extremely important, top quality stars have top quality color, pretty simple.
5. The legs of the star should be complete and sharp, with no missing or broken legs, and each ray should extend to the girdle of the stone.
6. The more transparent or translucent the stone the better. Tricky though, because sometimes with too much transparency the star is not evident.
How rare are these gems? For every 100 faceted corundum (ruby and sapphire) mined, approximately three stars are discovered. One will have good color and a bad star. One will have a great star and bad color. Only one out of a hundred will have a good star and good color.
Fine stars are pretty rare. Until the 1960s, these stones always sold for more than the faceted ruby.
1. Natural mined unheated star sapphires-
Star and color are natural
2. Heat Treated Star Sapphire-
Heat is used to enhance the color/clarity of the stone
3. Diffusion Star Sapphires-
Use of chemicals/heating on the surface of the stone to change the color or add a star to a stone that normally doesn't contain one
4. Linde Stars/Chatham Stars(Artificial/Lab Created Star Sapphires)-
Stone is synthetic material not a sapphire or ruby, star and color are artificially produced as well
5. Fracture Filled-
Oil, Glass, Resin or Epoxy fills cracks or fractures, usually unable to detect without optical instrumentation
How Can You As a consumer tell the difference? You Can't, It really takes a well equipped laboratory, to detect the intricate processes performed. My experience has been jewelers and most gemologists don't have the proper equipment to give you anything more than an educated guess. so if you have any question, send it to the AGTA, GIA or EGL gem lab, or a well recognized established lab.