Collecting unusual seals became popular among educated people, who often included bamboo root and intricately carved olive-pit seals in their collections.
紫檀木堅致、黃楊紋理細膩，都適合篆刻。但基本上木材容易腐朽，木質印保存十分困難。有人取竹節、竹根或橄欖核、瓜蒂來刻印，頗富奇趣。