"self lubricating", Spaw?...with what?...I thought they were simply extremely hard and smooth, thus reducing friction. Some woods (Lignumvitae, Verawood, Olive...etc.) have natural oils which make them naturally self-lubricating, and thus, prone to clog sandpaper badly...but having turned both Ivory and Ebony, I have never seen this happen.

Ebony does produce tiny, dusty residue (very much like graphite particles) when sanded, so I can see how it might seem like it was 'slick'....maybe that is all you meant...*shrug*