sluice box vs stain

sluice box

noun
  • A box with riffles along the bottom, used to trap heavier gold particles as water washes them and the other material along the box. 

stain

noun
  • A substance used to soak into a surface and colour it. 

  • A reagent or dye used to stain microscope specimens so as to make some structures visible. 

  • A discoloured spot or area. 

  • Any of a number of non-standard tinctures used in modern heraldry. 

  • A blemish on one's character or reputation. 

verb
  • To cause to seem inferior or soiled by comparison. 

  • To coat a surface with a stain 

  • To treat (a microscopic specimen) with a dye, especially one that dyes specific features 

  • To taint or tarnish someone's character or reputation 

  • To discolour. 

  • To become stained; to take a stain. 

How often have the words sluice box and stain occurred in a corpus of books? (source: Google Ngram Viewer )