Using stainless steel shot and soapy water on turquoise may work
well if the turquoise is stabilized, as the turquoise is then
well impregnated with acrylic plastic, and is both hard and
non-porous as a result. If the turquoise is untreated, it is
softer and absorbs water readily. Soapy water can discolor it
permanently, I have seen this first-hand. You might want to
make sure that the turquoise you are using is stabilized before
trying this.
Lee