A company in PA paid me for my share of mineral rights that my ancestor purchased in 1910. Is this taxable as ordinary income or capital gains?

I was not previously that I had rights to a share of these mineral rights. The amount paid for the purchase of the rights is less than $10,000. Is this taxable as ordinary income or capital gains? If I can report the income as capital gains, how do I compute the value of the inherited rights?

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