Take the finest sandstone you can find and make a cavity in the middle. And put in it an eighth part of ☿ and rub it and wear it down while adding some water with ☾ or ☼ until the material becomes paste—like and even harder. Then, if you want, corrode it with good aqua fortis, if it is ☾ or ♀. Then melt it again, having taken it out as you know. The ☾ will have some color, and after being melted it will leave some flecks of ☼, and the ♀ will be very fine and will have almost no covering.