Welcome to the forum. I pulled up the deed where you obtained these minerals, and it looks like they reside in the E/2 of the SW/4 of Section 26, Block 36, T2S, Glasscock County, TX. The "T2S" portion is important because there is more than one Section 26, Block 36 in Glasscock County.
Typically, unsolicited offers to buy minerals represent a small fraction of what they are actually worth. Your minerals are in a very active area. Pioneer is drilling a lot of Horizontal wells in the sections north of yours. (See map below)
If you are wanting to sell, my advice would be to contact one of the forum sponsors that may be able to assist you. They can probably give you some insight on what minerals are selling for in that area. You'll want to make sure that a purchase agreement makes it clear that the buyer has to pay you if the title examination reveals you own the amount of acreage they think you do. Some mineral buyers will use the "diligence review period" as a window to try to find someone to flip the minerals to. If they can't find a buyer, they'll point to some clause in the purchase agreement that will let them walk away. My advice is to not sell the minerals if you can ride it out and see what happens in the next few years. Best of luck!