Which size classifier do I get for flour gold ?

[GoldMine21]

Which classifier should I get for flour gold ? Choices I have are
1/100”, 1/70”, 1/50”, 1/30”, 1/20”, 1/12”, 1/8”, 1/4", 1/2“

 

[vpnavy]

Until someone pipes in - I searched

and found Classifiers (Nov 30, 2013, 04:16 PM)