We are told in Parashah Mishpatim (Exodus: 24:10) that Moshe beheld the throne of God: "...and under His feet was something like a sapphire brick." This unusual object is later divided into two separate 'stones' and brought down as the shnei luchot (or 'two tablets' of the covenant). Sapphire Magen David : The Sapphire Cube
This article goes on to show more approaches to the appropriateness of the concept that the Ten Commandments were written on sapphire cubes. https://www.facebook.com/video.php?v=10212325447359988
This article goes on to show more approaches to the appropriateness of the concept that the Ten Commandments were written on sapphire cubes. https://www.facebook.com/video.php?v=10212325447359988