Viewed from the back, the curved colour banding clearly visible in this flame fusion synthetic star sapphire. 

The same stone viewed from the front, with the curved colour banding more difficult to see. 

This is the rear view of a flame fusion synthetic ruby, which has been heated and then quenched in liquid to produce inclusions which mimic fingerprint & feather inclusions found in natural rubies.

This shot through table clearly shows the web-like appearance of the liquid inclusions in this quenched flame fusion synthetic ruby.

Another shot through table showing the liquid inclusions in this quenched flame fusion synthetic ruby. Inclusions similar to these are common in these stones.

Curved striae clearly visible in this flame fusion synthetic ruby.

Curved colour banding clearly visible in this flame fusion synthetic star sapphire.

Gas bubbles like those above, are another diagnostic inclusion in flame fusion synthetic sapphires and rubies.