Generally, the size that can be held in your hand can be cut out with a special grinder. If it is big, there is a special big slicer. Generally, there are places where gems are processed.

I don't quite understand what you said about the opacity below. According to my personal understanding, it may be because there is no polishing and there are many inclusions. Chemical methods will not be used for gem cutting. Cut off what you think is dirty, and then put it on the polishing wheel for polishing. You can use 1000 mesh first, and then add some diamond powder with the leather wheel to make the plane very bright.

This is the easiest way. However, if your crystal is relatively large, it is recommended to keep the weight and not cut it at will. Some gems win by quality, while others win by weight.