Is a sale of minerals in Oklahoma considered a capital gain for tax purposes?
The short answer is yes.
A sale of royalty or mineral interests in any state is considered a taxable event, and capital gains are paid.
The good news is that if you've held them long enough, your federal rate is a maximum of 15%.
It is possible to delay capital gains if you quality for a 1031 Exchange for other minerals, but this is pretty rare that someone would do this.