Gray Ooze

[The Archivist]

A seeping horror which closely resembles wet stone and is thus difficult-to detect. It will not be spread by non-harmful weapons, but it is subject only to lightening bolts or cuts and chops by weaponry, for it is impervious to cold or fire. It does not harm wood or stone, but it corrodes metal at the same rate that Black Pudding does. It does ,two dice of damage to exposed flesh for every turn it is in contact with it.

Not spread by non-harmful weapons but is spread by cuts or chops by weaponry. What are non-harmful weapons.  I interpret this as not spread by weapons a cleric can use but it is spread by all edged weapons.