An acre of surface is an acre of surface to me and someone who suggested to me that it was only worth 1/6th of an acres value would be told that I would never sell it to them. You have the right to partition, to split off your acres, your share of the surface, you can do this voluntarily with the cotenant/tennant in common or you could do it through the courts, it is your right. If it increases the value of your sirface acres by 500% it may also be good business. If the other party thinks that the surface acres would then be worth 6 times as much, they may offer you more than 1/6 of their value to avoid the hassle. You have the right to demand your acres be partitioned. I suggest that you not practically give your acres away at fire sale prices. You could still give them a fantastic deal at 1/2 price and receive 3 times as much. Do a little internet search and good luck.