Hi - thanks for your kind words! No, the onyx does not a special sealant. The stone supplier polishes the slab using a poly-resin coating, which keeps it sealed for many years. An important factor is to remember not to use any abrasive cleaning agents like powders - as they will scratch the surface. I think I would recommend using a good quality over the counter sealant to retreat it every 5 years or so.

Good luck!