I am looking for some advice and guidance for my mother. In January 2016, she sold her oil and gas mineral rights that were inherited from her parents in 2004 for $531,000. I understand that this will be taxed as a long term capital gain but I am having trouble figuring out at which percent? Her taxable income in 2015 was only her SS in the amount of about $18,000. In 2016, she only had her SS and the sale of the minerals. Also, when the minerals were inherited there was no value or cost basis assigned to the minerals so we don't know who or how to get that value either. Help we are struggling.... Thanks!