So if you just want to be on the safe side, you can make one on your own by using aluminum potassium sulfate or alum for short.

Since all forms of potassium alum are soluble in water, when the stone is wet or applied to wet skin, an invisible, fine layer of the mineral is rubbed off the stone and applied to the skins surface.

Ethyl decanoate was synthesized from capric acid and ethanol by using ferric potassium alum as catalyst.