I have been asked to hone a polished marble floor. At what grit is it considered honed?

There is no standard grit size that determines when marble is honed. Generally a 120 or 400 grit is honed, but this will vary from marble to marble. Perform several test patches and determine which grit will give you or your customer the appearance you are looking for.

FYI The term “hone” can be a confusing term in the stone restoration business. The correct definition of honing is to make smooth. A stone can be smooth as a 120 grit or it can be smooth at a 1800 grit.