Sometimes you find a diamond which is not a diamond; it is only a quartz crystal or some such worthless thing.

The expert can generally distinguish it from the precious stone which it is counterfeiting; but if he is in doubt he lays it on a flatiron and hits it with a sledgehammer.

If it is a diamond it holds its own; if it is anything else, it is reduced to powder.

I liked that experiment very much, and did not tire of repetitions of it.

It was full of enjoyable apprehensions, unmarred by any personal sense of risk.