Trillion cut ,sometimes called a trillion or trillian, is a triangular type of gemstone cut. The cut has many variations. It may have curved or uncurved sides. The shape of the top surface, or table, also varies. Now trillion cut become one of popular cuts for gemstones. This is a softer version of the uncurved version, with three soft points and curved sides. The length to width ratio should still be 1:1, keeping the gemstone proportioned. This cut is unusual, but can be found in pieces as a solitary gem or as an accent gem. Blue spinel look like blue sapphire and much cheaper than blue sapphire. So now many customers would you like to use lab blue spinel instead of blue sapphire. Here are some pictures of trillion cut blue spinel as for your reference.