Matters need attention:

1.use the indirect-vision method to estimate the hardness of the sample;

2.find a inconspicuous place,use the talc-l or plaster-2 to scratch the sample,if can't do,that means the sample's hardness is higher than the standard hardness pencil,so pls use the higher pencil to scratch,repetitive operation,if there is a shadow nick,that means the sample's hardness is amoust the same with the standard hardnedd pencil,then use the higher hardness pencil to scratch the gem,if there is a deep nick,means sample's hardness is lower than the standard hardness in this way,we can get the hardness of gem or the scope of hardness.

3.when you scratch,don't too heave or too light,just proper vigor

4.direct test method cost damage to the gem,so pls use it proper.generally speaking,we won't use this method to the finished gem.