It's absolutely massive!  The genuine Blue Topaz measures an incredible 38.5mm x 25mm. Please note that the stone does have natural imperfections that can be seen with the naked eye. This is common for a stone of this immense size. The imperfections do not take away from the overall  beauty, sparkle, and overall impressiveness of the gem. 

The mounting has been custom made to hold the substantial gemstone. It is of solid make and stamped 14k yellow gold.  The bail has an opening for a 5mm chain or omega.  It weighs an impressive 36.1g