In synthetic corundum, flux inclusions are often key indicators of the flux melt process used in its creation. This method can produce distinctive feather-like inclusions and hexagonal platinum platelets, which help identify the stone as synthetic rather than natural.
 |
| Photos: Gabriel Kleinberg and Pat Daly |
The Flux Melt Process
In the flux melt method, aluminium oxide (the base of corundum) is mixed with colouring elements like titanium and iron. The mixture is heated to high temperatures in a flux (a substance that helps the crystals form). As the solution cools slowly, corundum crystals begin to form, and during this cooling process, flux becomes trapped within the crystal, leading to the creation of translucent, feather-like inclusions.
 |
| Photos: Gabriel Kleinberg and Pat Daly |
Platinum Platelets in the Crucible
Additionally, the crucibleāthe container used to hold the molten materialāoften contains metals like platinum. During the process, platinum crystals from the crucible can be absorbed into the growing corundum crystal, forming hexagonal, opaque platelets. These inclusions have a metallic lustre and serve as another clue that the corundum is synthetic.
 |
| Photos: Gabriel Kleinberg and Pat Daly |
Identifying Synthetic Corundum
When evaluating synthetic corundum, the combination of feather-like inclusions and platinum platelets is a strong sign that the flux melt method was used. These distinctive markers set synthetic stones apart from natural corundum.