Sale, Option and Lease Agreements with Tonogold Resources Inc. ("Tonogold") Sale, Option and Lease Agreements with Tonogold Resources Inc. ("Tonogold")	6 Months Ended
Jun. 30, 2020
Equity Method Investments and Joint Ventures [Abstract]
Sale, Option and Lease Agreements with Tonogold Resources Inc. (Tonogold)	Sale, Option and Lease Agreements with Tonogold Resources Inc. ("Tonogold") There are three agreements between the Company and Tonogold: the Membership Purchase Agreement, the Mineral Exploration and Mining Lease, and a Lease Option Agreement for the Company's American Flat processing facility. Membership Interest Purchase Agreement On January 24, 2019, the Company entered into an agreement, as amended and restated on March 20, 2020, to sell its interests in Comstock Mining LLC (“CML”), its wholly-owned subsidiary whose sole net assets are the Lucerne properties and related permits, to Tonogold (the “Membership Purchase Agreement”), with the initial closing occurring on November 18, 2019. At the initial closing, Tonogold received 50% of the membership interests of CML, in exchange for the cash and CPS considerations paid to date. The Company retains all management control and authority over CML until Tonogold has made all remaining payments in full. Accordingly, Tonogold’s membership interest in CML is accounted for as a noncontrolling interest in the consolidated balance sheets. The Company has recorded the fair value received from Tonogold in excess of the non-controlling interest as additional paid in capital. For the six months ended June 30, 2020, the Company received an additional $0.6 million in cash payments, bringing the total cash consideration received to date to $6.525 million and the total stock consideration received to date to $6.1 million, in the form of Tonogold Convertible Preferred Stock ("CPS"). The CPS became convertible into Tonogold common shares on May 22, 2020. The conversion price for the CPS will be the lower of (1) 85% of the 20-day volume weighted closing price or (2) 0.18. Tonogold can redeem the CPS at any time prior to conversion, at a redemption price 120% of the face value of the CPS. On May 22, 2020, the Company exchanged $1.1 million of CPS for 6,111,111 common shares (at $0.18 per common share). The Company made its first sale of Tonogold common stock on June 19, 2020, and had sold 107,071 shares for net proceeds of $43,013 by June 30, 2020. Tonogold guaranteed the Company’s remaining financial responsibility for its membership interest in Northern Comstock LLC, which owns and leases certain mineral properties in the Lucerne area, and assumed certain reclamation liabilities, both totaling approximately $7.0 million. The Company also retains a 1.5% Net Smelter Returns ("NSR") royalty on the Lucerne properties. On March 20, 2020 the Company and Tonogold restated the Membership Purchase Agreement to secure the remaining cash consideration with a 12% secured convertible note with an initial principal balance of $5.475 million (the "Note"). The Note is initially secured by the membership interests held by Tonogold, and will be secured by all of CML's assets after the Company's debenture has been paid in full and the related liens released. Interest on the Note is payable on the first business day of each month, with a $1.0 million payment of principal due on or before October 15, 2020, and the remaining principal due at maturity on September 20, 2021. The Note is convertible into common shares of Tonogold, at the Company's sole option, at a conversion price equal to the lower of (1) 85% of the twenty (20) consecutive trading day volume weighted average price of Tonogold common stock or (2) an applicable price stepping from an initial $0.18 to $0.40 at the maturity date. On June 23, 2020, Tonogold made a payment of $0.5 million, originally due on or before October 15, 2020, toward the principal of the Note, increasing their membership interest ownership to 54.57%. Membership interest will be delivered proportionately to additional cash payments toward principal that are received. In a letter agreement dated June 30, 2020, the Company agreed to reduce the amount of the principal payment due on October 15, 2020, by $0.1 million. Interest will not accrue with respect to the $0.1 million principal reduction from June 30, 2020. Tonogold also agreed to pay up to an additional $0.3 million toward the reimbursement of additional expenses associated with certain mining properties. The remaining of $4.875 million of required cash consideration, after an incentivizing discount of $0.1 million for an early payment of $0.5 million in June 2020, is secured by a 12% Note (the "Note"), with interest payable monthly. In evaluating the accounting for the Note, the Company determined that although the Note represents legal form debt, it should be evaluated and accounted for based on the substance of the arrangement rather than its legal form. The Company concluded that the Note represents a contingent forward for the Company’s right to sell its membership interests in CML to Tonogold at a future date in exchange for consideration, cash or common stock of Tonogold if certain options are elected (the “Contingent Forward”). The Company accounts for the Contingent Forward at fair value because the Contingent Forward does not meet the requirements in ASC 815-40 to be accounted for in equity. The Company recorded the initial fair value of the Contingent Forward in additional paid in capital since Tonogold, as a related party, owns 50% of the membership interests of CML as a capital contribution. As a result, the Company has corrected the accounting for the initial fair value of the contingent forward of $1.2 million by recording the asset with a corresponding increase to Additional paid-in capital. All subsequent changes in the fair value of the contingent forward are recorded as a gain or loss in the statement of operations. The Company subsequently recorded the change in fair value for the period ended March 31, 2020 of $1.1 million in Change in estimated fair value of contingent forward asset, which had not been included in the previously issued financial statements as of and for the period ended March 31, 2020. Such corrections are reflected in the accompanying Condensed Consolidated Statement of Changes in Equity. The contingent forward has an aggregate fair asset value of $2.6 million at June 30, 2020. The Company recorded changes in the estimated fair value of the contingent forward of $0.4 million and $1.4 million for the three and six months ended June 30, 2020, respectively. Mineral Exploration and Mining Lease for Storey County Properties Effective September 16, 2019, the Company entered into a ten-year, renewable mineral lease with Tonogold for certain mineral properties owned or controlled by the Company in Storey County, Nevada (the "Exploration Lease"). The Exploration Lease grants Tonogold the right to use these properties for mineral exploration and development, and ultimately the production, removal and sale of minerals and certain other materials. Tonogold will pay a quarterly lease fee of $10 thousand. The lease fee will escalate 10% each year on the anniversary date of the Exploration Lease. Tonogold will also reimburse the Company for all costs associated with owning the properties. The Exploration Lease also provides for royalty payments after mining operations commence. For the first year following the commencement of mining, royalties will be paid at the rate of 3.0% of NSR for the properties. The rate will be reduced to 1.5% of NSR thereafter. The Company accounts for the Exploration Lease as an operating lease. On December 23, 2019, the Company and Tonogold restated the Exploration Lease. The restated Exploration Lease provides that Tonogold’s exploration spending, permitting, and engineering commitments are a minimum of $1 million per year, for a cumulative total of $20 million over 20 years. Tonogold also committed to specific milestones for issuing technical reports on their results, culminating in a published Feasibility report by the 20^th anniversary of the Exploration Lease. The initial term of the Exploration Lease (the "Exploration Term") is 5 years, with Tonogold committing to spending at least $5 million for exploration, at the rate of $1 million per year, and to producing an NI 43-101 compliant technical report by the end of the 5^th year. The Exploration Lease will automatically renew for a second, 10-year term (the "Development Term") as long as the commitments have been met. During the Development Term, Tonogold is committed to $10 million of additional expenditures for exploration, development, and technical reporting, at the rate of $1 million per year, and to producing an economically viable mine plan and an NI 43-101 compliant Pre-Feasibility report before the agreement's 15^th anniversary. The Exploration Lease will automatically renew for a third, 5-year term (“the Planning Term”) provided that the prior spending and reporting commitments have been met. During the Planning Term, Tonogold is committed to $5 million in additional expenditures for exploration, development, permitting, and technical reporting, at the rate of $1 million per year. By the 20^th anniversary of the agreement, Tonogold also commits to producing an economically viable mine plan, and an NI 43-101 compliant Feasibility report, and will produce a mutually agreed-upon schedule for placing the properties into production. If the spending and other commitments have been met during the Planning Term, the Exploration Lease will automatically continue in effect as long as development and permitting activities continue in compliance with a mutually agreed-upon schedule, or for so long as minerals are produced from the properties or from adjacent properties (the “Extended Term”). Lease Option Agreement for the American Flat Processing Facility On November 18, 2019, the Company entered into a lease-option to lease its permitted American Flat property, plant and equipment to Tonogold for crushing, leaching and processing material from the Lucerne mine (the "Lease Option Agreement"). Under the Lease Option Agreement, Tonogold will be required to reimburse the Company approximately $1.1 million in expenses, per year, to maintain the option. If such option is exercised, Tonogold will then pay the Company a rental fee of $1.0 million per year plus $1 per processed ton, in addition to all the costs of operating and maintaining the facility, up to and until the first $15.0 million in rental fees are paid, and then stepping down to $1.0 million per year and $0.50 per processed ton for the next $10.0 million paid to the Company. The Lease Option Agreement remains in effect, but has not yet been exercised. Other For the six-month period ended June 30, 2020, the Company received advance expense reimbursements from Tonogold totaling $2.3 million, and invoiced actual expense reimbursements totaling $1.2 million. The remaining $1.1 million is recorded as a Deposit in the liability section of the Balance Sheet.

On January 24, 2019, the Company entered into an agreement, as amended and restated on March 20, 2020, to sell its interests in Comstock Mining LLC (“CML”), its wholly-owned subsidiary whose sole net assets are the Lucerne properties and related permits, to Tonogold (the “Membership Purchase Agreement”), with the initial closing occurring on November 18, 2019.

At the initial closing, Tonogold received 50% of the membership interests of CML, in exchange for the cash and CPS considerations paid to date. The Company retains all management control and authority over CML until Tonogold has made all remaining payments in full. Accordingly, Tonogold’s membership interest in CML is accounted for as a noncontrolling interest in the consolidated balance sheets. The Company has recorded the fair value received from Tonogold in excess of the non-controlling interest as additional paid in capital.

For the six months ended June 30, 2020, the Company received an additional $0.6 million in cash payments, bringing the total cash consideration received to date to $6.525 million and the total stock consideration received to date to $6.1 million, in the form of Tonogold Convertible Preferred Stock ("CPS"). The CPS became convertible into Tonogold common shares on May 22, 2020. The conversion price for the CPS will be the lower of (1) 85% of the 20-day volume weighted closing price or (2) 0.18. Tonogold can redeem the CPS at any time prior to conversion, at a redemption price 120% of the face value of the CPS. On May 22, 2020, the Company exchanged $1.1 million of CPS for 6,111,111 common shares (at $0.18 per common share). The Company made its first sale of Tonogold common stock on June 19, 2020, and had sold 107,071 shares for net proceeds of $43,013 by June 30, 2020.

Tonogold guaranteed the Company’s remaining financial responsibility for its membership interest in Northern Comstock LLC, which owns and leases certain mineral properties in the Lucerne area, and assumed certain reclamation liabilities, both totaling approximately $7.0 million. The Company also retains a 1.5% Net Smelter Returns ("NSR") royalty on the Lucerne properties.

On March 20, 2020 the Company and Tonogold restated the Membership Purchase Agreement to secure the remaining cash consideration with a 12% secured convertible note with an initial principal balance of $5.475 million (the "Note"). The Note is initially secured by the membership interests held by Tonogold, and will be secured by all of CML's assets after the Company's debenture has been paid in full and the related liens released. Interest on the Note is payable on the first business day of each month, with a $1.0 million payment of principal due on or before October 15, 2020, and the remaining principal due at maturity on September 20, 2021. The Note is convertible into common shares of Tonogold, at the Company's sole option, at a conversion price equal to the lower of (1) 85% of the twenty (20) consecutive trading day volume weighted average price of Tonogold common stock or (2) an applicable price stepping from an initial $0.18 to $0.40 at the maturity date.

On June 23, 2020, Tonogold made a payment of $0.5 million, originally due on or before October 15, 2020, toward the principal of the Note, increasing their membership interest ownership to 54.57%. Membership interest will be delivered proportionately to additional cash payments toward principal that are received. In a letter agreement dated June 30, 2020, the Company agreed to reduce the amount of the principal payment due on October 15, 2020, by $0.1 million. Interest will not accrue with respect to the $0.1 million principal reduction from June 30, 2020. Tonogold also agreed to pay up to an additional $0.3 million toward the reimbursement of additional expenses associated with certain mining properties.

The remaining of $4.875 million of required cash consideration, after an incentivizing discount of $0.1 million for an early payment of $0.5 million in June 2020, is secured by a 12% Note (the "Note"), with interest payable monthly. In evaluating the accounting for the Note, the Company determined that although the Note represents legal form debt, it should be evaluated and accounted for based on the substance of the arrangement rather than its legal form. The Company concluded that the Note represents a contingent forward for the Company’s right to sell its membership interests in CML to Tonogold at a future date in exchange for consideration, cash or common stock of Tonogold if certain options are elected (the “Contingent Forward”). The Company accounts for the Contingent Forward at fair value because the Contingent Forward does not meet the requirements in ASC 815-40 to be accounted for in equity. The Company recorded the initial fair value of the Contingent Forward in additional paid in capital since Tonogold, as a related party, owns 50% of the membership interests of CML as a capital contribution.

As a result, the Company has corrected the accounting for the initial fair value of the contingent forward of $1.2 million by recording the asset with a corresponding increase to Additional paid-in capital. All subsequent changes in the fair value of the contingent forward are recorded as a gain or loss in the statement of operations. The Company subsequently recorded the change in fair value for the period ended March 31, 2020 of $1.1 million in Change in estimated fair value of contingent forward asset, which had not been included in the previously issued financial statements as of and for the period ended March 31, 2020. Such corrections are reflected in the accompanying Condensed Consolidated Statement of Changes in Equity. The contingent forward has an aggregate fair asset value of $2.6 million at June 30, 2020. The Company recorded changes in the estimated fair value of the contingent forward of $0.4 million and $1.4 million for the three and six months ended June 30, 2020, respectively.

Effective September 16, 2019, the Company entered into a ten-year, renewable mineral lease with Tonogold for certain mineral properties owned or controlled by the Company in Storey County, Nevada (the "Exploration Lease"). The Exploration Lease

Tonogold will pay a quarterly lease fee of $10 thousand. The lease fee will escalate 10% each year on the anniversary date of the Exploration Lease. Tonogold will also reimburse the Company for all costs associated with owning the properties. The Exploration Lease also provides for royalty payments after mining operations commence. For the first year following the commencement of mining, royalties will be paid at the rate of 3.0% of NSR for the properties. The rate will be reduced to 1.5% of NSR thereafter. The Company accounts for the Exploration Lease as an operating lease.

On December 23, 2019, the Company and Tonogold restated the Exploration Lease. The restated Exploration Lease provides that Tonogold’s exploration spending, permitting, and engineering commitments are a minimum of $1 million per year, for a cumulative total of $20 million over 20 years. Tonogold also committed to specific milestones for issuing technical reports on their results, culminating in a published Feasibility report by the 20^th anniversary of the Exploration Lease.

The initial term of the Exploration Lease (the "Exploration Term") is 5 years, with Tonogold committing to spending at least $5 million for exploration, at the rate of $1 million per year, and to producing an NI 43-101 compliant technical report by the end of the 5^th year. The Exploration Lease will automatically renew for a second, 10-year term (the "Development Term") as long as the commitments have been met. During the Development Term, Tonogold is committed to $10 million of additional expenditures for exploration, development, and technical reporting, at the rate of $1 million per year, and to producing an economically viable mine plan and an NI 43-101 compliant Pre-Feasibility report before the agreement's 15^th anniversary.

The Exploration Lease will automatically renew for a third, 5-year term (“the Planning Term”) provided that the prior spending and reporting commitments have been met. During the Planning Term, Tonogold is committed to $5 million in additional expenditures for exploration, development, permitting, and technical reporting, at the rate of $1 million per year. By the 20^th anniversary of the agreement, Tonogold also commits to producing an economically viable mine plan, and an NI 43-101 compliant Feasibility report, and will produce a mutually agreed-upon schedule for placing the properties into production.

If the spending and other commitments have been met during the Planning Term, the Exploration Lease will automatically continue in effect as long as development and permitting activities continue in compliance with a mutually agreed-upon schedule, or for so long as minerals are produced from the properties or from adjacent properties (the “Extended Term”).

On November 18, 2019, the Company entered into a lease-option to lease its permitted American Flat property, plant and equipment to Tonogold for crushing, leaching and processing material from the Lucerne mine (the "Lease Option Agreement"). Under the Lease Option Agreement, Tonogold will be required to reimburse the Company approximately $1.1 million in expenses, per year, to maintain the option. If such option is exercised, Tonogold will then pay the Company a rental fee of $1.0 million per year plus $1 per processed ton, in addition to all the costs of operating and maintaining the facility, up to and until the first $15.0 million in rental fees are paid, and then stepping down to $1.0 million per year and $0.50 per processed ton for the next $10.0 million paid to the Company. The Lease Option Agreement remains in effect, but has not yet been exercised.

For the six-month period ended June 30, 2020, the Company received advance expense reimbursements from Tonogold totaling $2.3 million, and invoiced actual expense reimbursements totaling $1.2 million. The remaining $1.1 million is recorded as a Deposit in the liability section of the Balance Sheet.