Melts into glowing sticky mass giving off various intensity of yellow/red light relative to speed and pressure applied. Sticks harder than anything you know to zirconia!
Diorite is not sticky at all, but pushes out a fine off white ash powder which forms little free dust. When heated to an extremely high temperature with the bit the diorite forms a red ceramic like coating similar to the mineral anorthosite
This rock is so hard and strong that it will melt or vaporize a ceramic tool. Diamond tooling however can cut through it like butter. Dioritic anorthosite can be thought of as chunks of machinable (alumina silicate)ceramics for lapidary purposes.
Melting limestone will produce shiny glass like black streaks.
Without issue can melt directly in at high RPM's. A thick black resin that hardens slowly is left behind. This is a very practical tool for a handheld pneumatic spindle.
Melts on contact with ease. Leaves a smooth slightly porous material behind. Ceramic tooling for this application could be expected to work better/safer than a torch.