I have used this white rocky substance recently in the making of two things; home made base cream and silver jewellery. Here it is on display in the Natural History Museum.
For the cosmetic, a teaspoon of powdered borax, dissolved in water, turns a melted mixture of cocoa butter, bees wax, almond oil and wheat germ oil in to a white cream.
In silver smithing, a hard stick of borax is ground down in a dish at the same time being mixed with water. We painted this milky liquid on to the small areas of silver that would be stuck together. A tiny piece of solder was balanced on joint and we torched it with a heat gun until the silver glowed rose and the solder ran liquid.
The face cream recipe was from a Neals Yard book and the silver smithing taught by Lara Mathers at The Papered Parlour