Corundum Doublets

The most likely place to find doublets and triplets is in antique jewelry. It is also possible to find doublets and triplets in new pieces.

Assembled stones normally consist of two parts (doublets) or three parts (triplets) glued together for the following reasons:

- to provide a better wearing surface.
- to obtain a large stone from two smaller pieces of natural gem material.
- to provide better color and appearance.

The purpose of producing corundum doublet is to have the careless buyer look into the table of the stone, see the natural inclusions on the crown area, then purchase the gem at a high price. This deception is possible because of the thin crown of colorless or light yellowish green sapphire does not influence the color the stone face up (table-up), which is determined by the synthetic material on the pavilion. Few buyers actually check the girdle of the stone. Corundum doublets are easy to detect if the buyer is aware of their features. The careless buyer can easily be fooled.

When you are trying to identify an unknown stone always suspect an assembled stone. To avoid the mother-of-all surprise you should look for the difference in color, luster or inclusions, plane of join, gas bubbles (if any) between the crown and pavilion (base) of the gem material. Doublets consisting of black star sapphire on the crown and pavilion of lower quality natural sapphire is also common. There is also doublet made of a base of a black, non-transparent layer of natural star sapphire topped with synthetic orange sapphire or synthetic spinel (flame fusion). Use good lighting and proper magnification to view the color contrast so that you are able to identify the stone.