Dang, I thought it was powdereed diamond
If memory serves, EQVE was added to test the code for moving powders. Since it only existed for that purpose, it wasn't programmed with any other properties or reactions, which makes it almost entirely useless. And it isn't indestructible, just non-flammable - you can still use BOMB on it, and probably things like DEST, SING, AMTR etc.