As described in David Warther's (his family has been working and selling ivory on and off since 1902) article on ivory working and preservation, I use light coats of pure mineral oil after sanding or cutting. Organic oils are specifically contraindicated for fear of staining, and because they go rancid over time. He further recommends renaissance wax for longer term protection.
With mechanical or gun oils, I might be concerned about solvent or detergent additives potentially degrading the material over time.
With mechanical or gun oils, I might be concerned about solvent or detergent additives potentially degrading the material over time.