Valuing Offer for Purchase of Mineral Rights

I received an offer to purchase the rights to ~0.3 mineral acres in Whiteley Township, Greene County, Pennsylvania. I realize that this is very small, but am wondering if anyone can provide me a rough estimate of fair value for the purchase of such rights. I understand that a lease may be better long-term but an considering this purchase offer given the relatively small size, and depending on what I can ascertain as the value for the purchase.

Additionally for what it is worth, the offer came unsolicited to me and must have come to me through some unknown inheritance as I do not reside in PA and know of no ownership (nor family ties) to that area, and further the mineral rights interest is ~1% of the total gross acreage noted in the paperwork provided.

Thank you

somewhere between 1500-2000

My mother was sent papers from a oil and gas acquisition company cause her grandfather and brother owns mineral rights in Pennsylvania in Greene county. The offer is way below $1500 per acre when divided up among the supposed 24 heirs they contacted. There is a little over 104 acres and they want to pay less than $2000 to her. She only has mineral rights nog surface rights, her grandfather and his brother sold or gave the land to others but not the mineral rights. Does anybody know what a fair and resonable offer would be that she could get? I just dont want her getting taken advantage of and she can’t afford a attorney.