Exhibit 99.1

APPENDIX “L”

HECLA AND KLONDEX UNAUDITED PRO FORMA CONDENSED

COMBINED FINANCIAL STATEMENTS

The following unaudited pro forma condensed combined financial statements (the “Pro Forma Statements”) give effect to the proposed Arrangement and represent the Combined Company’s unaudited pro forma condensed combined balance sheet as of March 31, 2018 and the Combined Company’s unaudited pro forma condensed combined statements of operations for the three months ended March 31, 2018 and the year ended December 31, 2017. The unaudited pro forma condensed combined balance sheet gives effect to the proposed Arrangement (as defined herein) as if it had occurred on the date of such balance sheet. The accompanying unaudited pro forma condensed combined statements of operations give effect to the proposed Arrangement as if it had occurred on January 1, 2017.

For accounting purposes, the transaction would be accounted for using the acquisition method, pursuant to which assets and liabilities are recorded at fair value. The valuation of Hecla’s shares to be issued as consideration was based upon an assumed closing price of Hecla’s common stock of $3.94. See Note 2 to these Pro Forma Statements for additional information on the estimated purchase consideration and the impact thereon of changes in the per share price of our stock.

The unaudited pro forma condensed combined balance sheet and statements of operations should be read in conjunction with the historical financial statements of Hecla and Klondex including the notes thereto, which are included in their respective Quarterly Reports filed on Form 10-Q for the three months ended March 31, 2018 and Annual Reports filed on Form 10-K for the year ended December 31, 2017, which are incorporated by reference in this Circular.

The Pro Forma Statements are not necessarily indicative of the operating results or financial condition that would have been achieved if the proposed Arrangement had been completed on the dates or for the periods presented, nor do they purport to project the results of operations or financial position of the combined entities for any future period or as of any future date. Actual amounts recorded upon consummation of the proposed Arrangement would likely differ from those recorded in the Pro Forma Statements. The Pro Forma Statements do not reflect any special items such as integration costs or operating synergies that may be realized as a result of the proposed Arrangement.

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Hecla Mining Company

Unaudited Pro Forma Condensed Combined Balance Sheet

As of March 31, 2018

(in thousands)

See accompanying notes to these unaudited pro forma condensed combined financial statements.

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Hecla Mining Company

Unaudited Pro Forma Condensed Combined Statement of Operations

For the three months ended March 31, 2018

(in thousands, except per share amounts)

See accompanying notes to these unaudited pro forma condensed combined financial statements.

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Hecla Mining Company

Unaudited Pro Forma Condensed Combined Statement of Operations

For the year ended December 31, 2017

(in thousands, except per share amounts)

See accompanying notes to these unaudited pro forma condensed combined financial statements.

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NOTES TO THE UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL STATEMENTS

Note 1. Basis of presentation

Hecla Mining Company (“Hecla”) and Klondex Mines Ltd. (“Klondex”) entered into an Arrangement pursuant to which Hecla would acquire all of the issued and outstanding common shares of Klondex (see Note 2 for more information). It is assumed the Arrangement would be accounted for as a business combination. The Pro Forma Statements are prepared on that basis and are presented to give effect to the proposed Arrangement of all of the outstanding common shares of Klondex by Hecla. The Pro Forma Statements represent the Combined Company’s unaudited pro forma condensed combined balance sheet as of March 31, 2018, and unaudited pro forma condensed combined statements of operations for the three months ended March 31, 2018 and the year ended December 31, 2017. The unaudited pro forma condensed combined balance sheet gives effect to the proposed Arrangement as if it occurred on the date of such balance sheet. The unaudited pro forma condensed combined statements of operations give effect to the proposed Arrangement as if it occurred on January 1, 2017. The Pro Forma Statements reflect the acquisition of assets, assumptions of liabilities, and operating activities relating to Klondex’s Nevada properties, and not Klondex’s Canadian properties, as Klondex’s Canadian assets would be held by a newly formed entity and not retained by the Combined Company as a result of the proposed Arrangement. Historical information for Hecla and Klondex has been derived from historical consolidated financial statements, which were prepared and presented in accordance with United States Generally Accepted Accounting Principles (“GAAP”). The pro forma adjustments and allocations of the estimated consideration that would be transferred are based on preliminary estimates of the fair value of assets to be acquired, liabilities to be assumed, and consideration to be transferred. As of the date of this Circular, the proposed Arrangement has not yet been completed. The final determination of the consideration transferred and the related allocation would be completed after asset and liability valuations are finalized as of the date of completion of the proposed Arrangement. Changes to these adjustments may materially affect both the estimated value of the consideration transferred and the preliminary estimated fair value to the assets and liabilities as presented in the Pro Forma Statements.

In preparing the unaudited pro forma condensed combined balance sheet and statements of operations in accordance with GAAP, the following historical information was used:

The unaudited pro forma condensed combined balance sheet and statements of operations should be read in conjunction with the historical financial statements including the notes thereto, as listed above, which are incorporated by reference in this Circular. All amounts are stated in U.S. dollars unless otherwise noted.

Note 2. Description of the Arrangement

On March 16, 2018, Hecla and Klondex entered into an Arrangement Agreement pursuant to which Hecla would acquire all of the issued and outstanding common shares of Klondex for consideration valued at $2.47 per share. Under the terms of the proposed Arrangement, each holder of Klondex common shares may elect to receive either (i) US$2.47 in cash (the “Cash Alternative”), (ii) 0.6272 of a Hecla share per Klondex share (the “Share Alternative”), or (iii) US$0.8411 in cash and 0.4136 of a Hecla share per Klondex share (the “Combined Alternative”), subject in the case of the Cash Alternative and the Share Alternative to pro-ration based on a maximum total cash consideration of approximately $157.4 million and a maximum total number of Hecla shares issued of 77,411,859. If all Klondex shareholders elect either the Cash Alternative or the Share Alternative, each Klondex shareholder would be entitled to receive US$0.8411 in cash and 0.4136 Hecla shares. Klondex shareholders would also receive shares of a newly formed company which would hold the Canadian assets of

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Klondex. Klondex had 179,668,072 issued and outstanding common shares as of May 7, 2018. An additional 7,476,924 Klondex common shares would be issued immediately prior to consummation of the proposed Arrangement related to conversion of in-the-money Klondex share options and warrants and certain outstanding restricted share units, resulting in a total of 187,144,996 issued and outstanding Klondex common shares at the time of consummation of the proposed Arrangement. For financial accounting purposes, the purchase price allocation is based upon the assumption of Hecla paying $157.4 million in cash and issuing 77,411,859 shares of Hecla common stock having a total value of $304.9 million, for total consideration of $462.3 million. The pro forma value of Hecla stock issued as consideration was based upon the 60-day volume-weighted average price at the time of announcement on March 19, 2018 of $3.94 per share. The closing price of Hecla’s common stock was $3.97 at May 7, 2018.

The following represents the preliminary estimated allocation of the consideration to be transferred as if the proposed Arrangement had occurred on March 31, 2018:

The actual value of consideration transferred would be based on the market price of Hecla’s common stock on the date the proposed Arrangement is consummated. A 10% change in the price per share of Hecla stock would result in an approximate $30.5 million change in the amount of total consideration transferred in the Arrangement.

Note 3. Effect of the Arrangement on the unaudited pro forma condensed combined balance sheet

The unaudited pro forma condensed combined balance sheet includes the following adjustments:

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In connection with the proposed Arrangement, Hecla is also expected to issue 2,068,000 warrants to purchase one share of Hecla’s common stock (“Hecla Warrants”) to a holder of warrants to purchase Klondex’s common stock. The Hecla Warrants would have an exercise price of CAD$5.47 less the Canadian dollar equivalent of US$0.8411, all divided by 0.4136, and would expire in April 2032. The accounting treatment of the Hecla Warrants is being evaluated, and no adjustment has been made to unaudited pro forma condensed combined balance sheet for the Hecla Warrants. However, it is expected that such adjustment would not have a material effect on the Pro Forma Statements.

No adjustment has been made to the unaudited pro forma condensed combined statements of operations for the preliminary estimated fair value adjustment for product inventory. This adjustment, which would decrease the pro forma net income for the three months ended March 31, 2018 by $9.6 million and increase the pro forma net loss for the year ended December 31, 2017 by approximately $3.5 million, is non-recurring.

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Note 4. The effect of the Arrangement on the unaudited pro forma condensed combined statements of operations

The following is information on the unaudited pro forma condensed combined statements of operations:

Note 5. Share capital

The following is information on the pro forma share capital of the Combined Company which gives effect to common shares of Hecla that would be issued under the proposed Arrangement:

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Note 6. Earnings per share

For purposes of the Pro Forma Statements, earnings per share has been calculated using the weighted average number of common shares which would have been outstanding for the three months ended March 31, 2018 and the year ended December 31, 2017 after giving effect to the Arrangement as if it had occurred on January 1, 2017. The following is information on pro forma basic and diluted weighted average common shares outstanding:

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