Make friction with each other, The true Pearl results in acerbity with powder while the false will be somewhat smooth without powder;
The true Pearl feels cool and comfortable but the false doesn't;
Scratch with knife, Powder appears for true Pearl and remains good but false will peel off;
Gnaw with teeth slightly, True Pearl will be with coarse surface and astringent but the false will feel lubricous and with teeth dents or peeling off;