Bowenite
Hardness is not a good test. Nephrite is 6 to 6i/2, and jadeite 61/2 to 7. Then, too, there is a variety of good green serpentine, called bow-enite, which looks very much like nephrite and has a hardness of 6. These hardnesses are all too close for certainty. The old trick of making a small, inconspicuous scratch with a penknife will not distinguish jadeite from nephrite, and will not eliminate bowenite or other hard species. It is useful for separating out the softer varieties of serpentine, soapstone, etc. Specific-gravity determinations are good, in that they do not require any mutilation of a carving.
The entire piece can be measured. Fortunately, too, jadeite has a specific gravity of 3.3 to 3.5, and nephrite of 2.96 to 3.10. The gap is sufficient to measure and distinguish one from another. But once again, bowenite, with a specific gravity just under 3.0, confuses nephrite identifications. Visual examination sometimes helps, because the expert soon comes to recognize a certain crystallinity in jadeite that is lacking in the other stones. Nephrite and serpentine have an amorphous internal appearance. A polished surface on nephrite seems to look more oily than glassy.