1. Summary of Significant Accounting Policies and Business Operations (Details)	9 Months Ended
	Sep. 30, 2021
Details
Entity Incorporation, Date of Incorporation	Nov. 09, 1935
Nature of Operations	In April 1978, the Montgomery Mines Corporation was obtained by a group of the Thunder Mountain property holders and changed its name to Thunder Mountain Gold, Inc., with the primary goal to further develop their holdings in the Thunder Mountain Mining District, located in Valley County, Idaho. Thunder Mountain Gold, Inc. takes its name from the Thunder Mountain Mining District, where its principal lode mining claims were located. For several years, the Company’s activities were restricted to maintaining its property position and exploration activities. During 2005, the Company sold its holdings in the Thunder Mountain Mining District. During 2007, the Company acquired the South Mountain Mines property in southwest Idaho and initiated exploration activities on that property, which continue today.
Going Concern	The Company has historically incurred losses, however, under the BeMetals Option Agreement (Note 3), the Company now has a recurring source of revenue, and its ability to continue as a going concern is no longer dependent on equity capital raises and borrowings.
Substantial Doubt about Going Concern, Management's Evaluation	if necessary, the Company continues to have the ability to raise additional capital to fund its future exploration and working capital requirements. The Company’s plans for the long-term continuation as a going concern include operating on the cash flows and consideration payments provided under the BeMetals Option Agreement.