Change in Accounting Principle	12 Months Ended
Dec. 31, 2018
Change in Accounting Principle
Change in Accounting Principle	4. Change in Accounting Principle Warrant Liability In July 2017, the FASB issued ASU 2017-11, “Earnings Per Share (Topic 260); Distinguishing Liabilities from Equity (Topic 480); Derivatives and Hedging (Topic 815): (Part 1) Accounting for Certain Financial Instruments with Down Round Features, (Part II) Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and Certain Mandatorily Redeemable Noncontrolling Interests with a Scope Exception” (“ASU 2017-11”). Part I relates to the accounting for certain financial instruments with down round features in Subtopic 815-40, which is considered in determining whether an equity-linked financial instrument qualifies for a scope exception from derivative accounting. Down round features are features of certain equity-linked instruments (or embedded features) that result in the strike price being reduced based on the pricing of future equity offerings. An entity still is required to determine whether instruments would be classified in equity under the guidance in Subtopic 815-40 in determining whether they qualify for that scope exception. If they do qualify, freestanding instruments with down round features are no longer classified as liabilities. In the case where the exception from derivative accounting does not apply, warrants must be accounted for as a liability and recorded at fair value at the date of grant and re-valued at the end of each reporting period. The September 2012 and 2014 warrants (see Note 15) include anti-dilution provisions characterized as down round features and were previously accounted for as liabilities, with the fair value of the warrant liabilities remeasured at each reporting date and the change in liabilities recorded as other non-operating income or loss. The Company had recorded a warrant liability of $1.5 million as of September 30, 2017 and reported a warrant derivative loss of $0.4 million for the nine months ended September 30, 2017 relating to the September 2012 and 2014 warrants prior to the change in accounting principle. In addition, for freestanding equity-classified financial instruments, ASU 2017-11 also requires entities that present earnings per share (EPS) in accordance with Topic 260 to recognize the effect of the down round feature when it is triggered. That effect is treated as a dividend and as a reduction of income available to common shareholders in basic EPS. Certain equity transactions following the issuance of the September 2012 and 2014 warrants have triggered anti-dilution clauses in the warrant agreements resulting in additional warrant shares and a reduction to the original strike price of the warrants. ASU 2017-11 prescribes a method to measure the value of a deemed dividend related to a triggering event by computing the difference in fair value between two instruments that have terms consistent with the actual instrument but that do not have a down round feature, where the number of warrant shares and strike price of one instrument corresponds to the actual instrument before the triggering event and the number of warrant shares and strike price of the other instrument corresponds to the actual instrument immediately after the triggering event. Following ASU 2017-11, for periods ending on or prior to December 31, 2016 the Company would have reduced its “Accumulated deficit” as reported on its Consolidated Balance Sheets by approximately $0.3 million related to prior triggering events. During the nine-month period ending September 30, 2017 the Company would have reduced its accumulated deficit by approximately $3,000 related to triggering events. During the year ending December 31, 2018 the Company reduced its accumulated deficit by approximately $8,000 related to triggering events. Except for the down round features in the September 2012 and 2014 warrants, the warrants would have been classified in equity under the guidance in Subtopic 815-40 and therefore qualify for the scope exception in ASU 2017-11. As permitted, the Company elected to adopt the accounting principles prescribed by ASU 2017-11 during the interim period ended September 30, 2017 and recorded a cumulative-effect adjustment stemming from a change in accounting principle in its financial statements measured retrospectively to the beginning of 2017. The cumulative effect adjustment appears at the beginning of 2017 in the Company’s Consolidated Statement of Changes in Equity. The results of operations for the Company for the three months ended March 31, 2017 reflect application of the change in accounting principle from the beginning of 2017. As noted above, the Company had previously reported a warrant derivative gain of $0.4 million during the nine-month period ending September 30, 2017. Because the Company has retroactively applied the change in accounting principle discussed above to the beginning of 2017, the Company is no longer reporting warrant derivative gains or losses for the September 2012 and 2014 warrants beginning in 2017. Other Income Related to the Sale of Exploration Properties During the first quarter 2018 the Company adopted ASU No. 2014-09, “Revenue from Contracts with Customers (Topic 606)” (“ASU 2014-09”) which was issued by the FASB” in May 2014. ASU 2014-09 outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. In addition, the guidance requires improved disclosures to help users of financial statements better understand the nature, amount, timing and uncertainty of revenue that is recognized and the related cash flows. The Company has elected the modified retrospective method of initially adopting ASU 2014-09. ASU 2014-09 requires, in certain instances, that transactions covered by ASC Topic 610, “Other Income” (“Topic 610”) follow the recognition, measurement and disclosure guidelines established by ASU 2014-09. The Company generally follows the guidance of Topic 610 with respect to the recognition of income from the farm-out or sale of exploration properties. As of the beginning of 2018, the Company had one open contract impacted by the adoption of ASU 2014-09, involving an option agreement under which Santacruz Silver Mining Ltd. (“Santacruz”) may acquire the Company’s interest in certain nonstrategic mineral claims located in the Zacatecas Mining District, Zacatecas, Mexico (the “Zacatecas Properties”) for a series of payments totaling $1.5 million (Note 9). In applying ASU 2014-09, approximately $49,000 of the income recognized from the Santacruz transaction in the fourth quarter of 2017 would have been recognized in the first quarter of 2018. Accordingly, the Company has recognized retrospectively the cumulative effect of initially adopting ASU 2014-09 by recording a negative adjustment to retained earnings of $49,000 at the beginning of 2018, included in the Company’s Consolidated Statement of Changes in Equity, and recording $49,000 in “Other operating income, net” in the accompanying Consolidated Statements of Operations and Comprehensive Loss for the period ended December 31, 2018. See Note 9 for a further description of the contract with Santacruz and the identification of performance obligations and other significant judgments used in applying the guidance of Topic 606 to the contract. Available for Sale Securities During the first quarter 2018 the Company adopted ASU No. 2016-01, which amended its accounting treatment for the recognition, measurement, presentation and disclosure of certain financial assets. ASU 2016-01 requires equity investments that have readily determinable fair values to be measured at fair value through net income. Previously, entities would recognize changes in fair value of available-for-sale equity securities in other comprehensive income and would recognize in net income impairment losses that were other-than-temporary. There will no longer be an available-for-sale classification (with changes in fair value reported in other comprehensive income) for equity securities with readily determinable fair values. At December 31, 2017, the Company had equity securities classified as available-for-sale and reported at fair value of $238,000, with cumulative unrealized losses of $40,000 recorded in “Accumulated other comprehensive loss” on its Consolidated Balance Sheets. The Company has recognized the cumulative effect of initially adopting ASU 2016-01 by recording a negative adjustment to retained earnings and other comprehensive income of $40,000 at the beginning of 2018, included in the Company’s Consolidated Statement of Changes in Equity, and has recorded a gain of approximately $51,000 in “Interest and other income, net” in the accompanying Consolidated Statements of Operations and Comprehensive Loss for the period ended December 31, 2018.

4. Change in Accounting Principle

Warrant Liability

In July 2017, the FASB issued ASU 2017-11, “Earnings Per Share (Topic 260); Distinguishing Liabilities from Equity (Topic 480); Derivatives and Hedging (Topic 815): (Part 1) Accounting for Certain Financial Instruments with Down Round Features, (Part II) Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and Certain Mandatorily Redeemable Noncontrolling Interests with a Scope Exception” (“ASU 2017-11”). Part I relates to the accounting for certain financial instruments with down round features in Subtopic 815-40, which is considered in determining whether an equity-linked financial instrument qualifies for a scope exception from derivative accounting. Down round features are features of certain equity-linked instruments (or embedded features) that result in the strike price being reduced based on the pricing of future equity offerings. An entity still is required to determine whether instruments would be classified in equity under the guidance in Subtopic 815-40 in determining whether they qualify for that scope exception. If they do qualify, freestanding instruments with down round features are no longer classified as liabilities. In the case where the exception from derivative accounting does not apply, warrants must be accounted for as a liability and recorded at fair value at the date of grant and re-valued at the end of each reporting period.

The September 2012 and 2014 warrants (see Note 15) include anti-dilution provisions characterized as down round features and were previously accounted for as liabilities, with the fair value of the warrant liabilities remeasured at each reporting date and the change in liabilities recorded as other non-operating income or loss. The Company had recorded a warrant liability of $1.5 million as of September 30, 2017 and reported a warrant derivative loss of $0.4 million for the nine months ended September 30, 2017 relating to the September 2012 and 2014 warrants prior to the change in accounting principle.

In addition, for freestanding equity-classified financial instruments, ASU 2017-11 also requires entities that present earnings per share (EPS) in accordance with Topic 260 to recognize the effect of the down round feature when it is triggered. That effect is treated as a dividend and as a reduction of income available to common shareholders in basic EPS. Certain equity transactions following the issuance of the September 2012 and 2014 warrants have triggered anti-dilution clauses in the warrant agreements resulting in additional warrant shares and a reduction to the original strike price of the warrants. ASU 2017-11 prescribes a method to measure the value of a deemed dividend related to a triggering event by computing the difference in fair value between two instruments that have terms consistent with the actual instrument but that do not have a down round feature, where the number of warrant shares and strike price of one instrument corresponds to the actual instrument before the triggering event and the number of warrant shares and strike price of the other instrument corresponds to the actual instrument immediately after the triggering event. Following ASU 2017-11, for periods ending on or prior to December 31, 2016 the Company would have reduced its “Accumulated deficit” as reported on its Consolidated Balance Sheets by approximately $0.3 million related to prior triggering events. During the nine-month period ending September 30, 2017 the Company would have reduced its accumulated deficit by approximately $3,000 related to triggering events. During the year ending December 31, 2018 the Company reduced its accumulated deficit by approximately $8,000 related to triggering events.

Except for the down round features in the September 2012 and 2014 warrants, the warrants would have been classified in equity under the guidance in Subtopic 815-40 and therefore qualify for the scope exception in ASU 2017-11. As permitted, the Company elected to adopt the accounting principles prescribed by ASU 2017-11 during the interim period ended September 30, 2017 and recorded a cumulative-effect adjustment stemming from a change in accounting principle in its financial statements measured retrospectively to the beginning of 2017. The cumulative effect adjustment appears at the beginning of 2017 in the Company’s Consolidated Statement of Changes in Equity. The results of operations for the Company for the three months ended March 31, 2017 reflect application of the change in accounting principle from the beginning of 2017. As noted above, the Company had previously reported a warrant derivative gain of $0.4 million during the nine-month period ending September 30, 2017. Because the Company has retroactively applied the change in accounting principle discussed above to the beginning of 2017, the Company is no longer reporting warrant derivative gains or losses for the September 2012 and 2014 warrants beginning in 2017.

Other Income Related to the Sale of Exploration Properties

During the first quarter 2018 the Company adopted ASU No. 2014-09, “Revenue from Contracts with Customers (Topic 606)” (“ASU 2014-09”) which was issued by the FASB” in May 2014. ASU 2014-09 outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. In addition, the guidance requires improved disclosures to help users of financial statements better understand the nature, amount, timing and uncertainty of revenue that is recognized and the related cash flows. The Company has elected the modified retrospective method of initially adopting ASU 2014-09.

ASU 2014-09 requires, in certain instances, that transactions covered by ASC Topic 610, “Other Income” (“Topic 610”) follow the recognition, measurement and disclosure guidelines established by ASU 2014-09. The Company generally follows the guidance of Topic 610 with respect to the recognition of income from the farm-out or sale of exploration properties. As of the beginning of 2018, the Company had one open contract impacted by the adoption of ASU 2014-09, involving an option agreement under which Santacruz Silver Mining Ltd. (“Santacruz”) may acquire the Company’s interest in certain nonstrategic mineral claims located in the Zacatecas Mining District, Zacatecas, Mexico (the “Zacatecas Properties”) for a series of payments totaling $1.5 million (Note 9). In applying ASU 2014-09, approximately $49,000 of the income recognized from the Santacruz transaction in the fourth quarter of 2017 would have been recognized in the first quarter of 2018. Accordingly, the Company has recognized retrospectively the cumulative effect of initially adopting ASU 2014-09 by recording a negative adjustment to retained earnings of $49,000 at the beginning of 2018, included in the Company’s Consolidated Statement of Changes in Equity, and recording $49,000 in “Other operating income, net” in the accompanying Consolidated Statements of Operations and Comprehensive Loss for the period ended December 31, 2018. See Note 9 for a further description of the contract with Santacruz and the identification of performance obligations and other significant judgments used in applying the guidance of Topic 606 to the contract.

Available for Sale Securities

During the first quarter 2018 the Company adopted ASU No. 2016-01, which amended its accounting treatment for the recognition, measurement, presentation and disclosure of certain financial assets. ASU 2016-01 requires equity investments that have readily determinable fair values to be measured at fair value through net income. Previously, entities would recognize changes in fair value of available-for-sale equity securities in other comprehensive income and would recognize in net income impairment losses that were other-than-temporary. There will no longer be an available-for-sale classification (with changes in fair value reported in other comprehensive income) for equity securities with readily determinable fair values. At December 31, 2017, the Company had equity securities classified as available-for-sale and reported at fair value of $238,000, with cumulative unrealized losses of $40,000 recorded in “Accumulated other comprehensive loss” on its Consolidated Balance Sheets. The Company has recognized the cumulative effect of initially adopting ASU 2016-01 by recording a negative adjustment to retained earnings and other comprehensive income of $40,000 at the beginning of 2018, included in the Company’s Consolidated Statement of Changes in Equity, and has recorded a gain of approximately $51,000 in “Interest and other income, net” in the accompanying Consolidated Statements of Operations and Comprehensive Loss for the period ended December 31, 2018.