UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D/A

Under the Securities Exchange Act of 1934
(Amendment No. 15)*

PolyMet Mining Corp.

(Name of Issuer)

Common Shares, without par value

(Title of Class of Securities)

731916102

(CUSIP Number)

Stephen Rowland and Rajiv Singhal

Glencore International AG

Baarermattstrasse 3

CH-6341 Baar

Switzerland

+41 41 709 2000

With copies to:

Matias Vega, Esq.

Curtis, Mallet-Prevost, Colt & Mosle LLP

101 Park Avenue

New York, NY 10178

(212) 696-6000

(Name, Address and Telephone Number of Person
Authorized to Receive Notices and Communications)

April 25, 2014

(Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box. [ ]

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See §240.13d-7 for other parties to whom copies are to be sent.

^* The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

CUSIP No. 731916102

CUSIP No. 731916102

CUSIP No. 731916102

Explanatory Note:

This Amendment No. 15 (this “Amendment No. 15”) amends and restates the Schedule 13D originally filed with the United States Securities and Exchange Commission (the “SEC”) by Glencore Holding AG, Glencore International AG and Glencore AG on November 10, 2008, and amended by Amendment No. 1 thereto filed on December 24, 2008, Amendment No. 2 thereto filed on June 22, 2009, Amendment No. 3 thereto filed on September 4, 2009, Amendment No. 4 thereto filed on November 3, 2009, Amendment No. 5 thereto filed on November 23, 2009, Amendment No. 6 thereto filed on January 27, 2010, Amendment No. 7 thereto filed on November 15, 2010, Amendment No. 8 thereto filed on June 2, 2011 (which amendment removed Glencore Holding AG as a Reporting Person and added Glencore International plc (now known as Glencore Xstrata plc) as a Reporting Person), Amendment No. 9 thereto filed on July 15, 2011, Amendment No. 10 thereto filed on December 6, 2011, Amendment No. 11 thereto filed on October 16, 2012, Amendment No. 12 thereto filed on April 16, 2013, Amendment No. 13 thereto filed on June 10, 2013 and Amendment No. 14 thereto filed on July 8, 2013 (as so amended, the “Statement”) relating to the common shares, no par value (“Common Shares”), of PolyMet Mining Corp., a corporation incorporated under the laws of the Province of British Columbia, Canada (the “Issuer”). This Amendment No. 15 reflects changes to Items 3, 5, and 7 of the Statement.

Item 1 Security and Issuer

This Schedule 13D relates to the common shares, without par value (the “Common Shares”), of PolyMet Mining Corp., a corporation incorporated under the laws of the Province of British Columbia, Canada. The Issuer’s principal executive office is located at First Canadian Place, 100 King Street West, Suite 5700, Toronto, Ontario Canada M5X 1C7.

Item 2 Identity and Background

This Schedule 13D is being filed by (a) Glencore Xstrata plc (“Glencore plc”), (b) Glencore International AG (“Glencore International”) and (c) Glencore AG (collectively, the “Reporting Persons”). Glencore plc is a company organized under the laws of Jersey. Each of Glencore International and Glencore AG is a company organized under the laws of Switzerland.

Glencore plc is a public company with its ordinary shares listed on the London Stock Exchange and on the Hong Kong Stock Exchange. Glencore plc is the parent company of Glencore International which, together with its subsidiaries, including Glencore AG, is a leading integrated producer and marketer of commodities, with worldwide activities in the marketing of metals and minerals, energy products and agricultural products and the production, refinement, processing, storage and transport of these products. Each of the Reporting Persons other than Glencore plc is a direct or indirect wholly-owned subsidiary of Glencore plc. Glencore AG is a direct wholly-owned subsidiary of Glencore International.

The address of the principal business and office of each of the Reporting Persons is Baarermattstrasse 3, CH-6341 Baar, Switzerland.

The name, citizenship, occupation and principal business address of each director and executive officer of the Reporting Persons are listed in Schedule 1 hereto (the “Schedule 1 Persons”), which Schedule 1 is incorporated herein by reference.

During the last five years, none of the Reporting Persons, or, to the Reporting Persons’ knowledge, any of the Schedule 1 Persons, has been (i) convicted in a criminal proceeding (excluding traffic violations and similar misdemeanors) or (ii) party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

Item 3. Source and Amount of Funds or Other Consideration

On October 31, 2008, Glencore AG, the Issuer and the Issuer’s wholly owned subsidiary, Poly Met Mining, Inc., a Minnesota corporation (the “Issuer Subsidiary”), entered into a purchase agreement (the “Original Purchase Agreement”), as amended by a letter agreement (“Amendment No. 1”), dated as of November 28, 2008, and as further amended by a letter agreement (“Amendment No. 2”), dated as of December 12, 2008, a letter agreement (“Amendment No. 3”), dated as of December 19, 2008, a letter agreement (“Amendment No. 4”), dated as of January 30, 2009, a letter agreement (“Amendment No. 5”), dated as of February 24, 2009, a letter agreement (“Amendment No. 6”), dated as of March 30, 2009, a letter agreement (“Amendment No. 7”), dated as of April 28, 2009, a letter agreement (“Amendment No. 8”), dated as of June 4, 2009, a letter agreement (“Amendment No. 9”), dated as of August 31, 2009, a letter agreement (“Amendment No. 10”), dated as of October 20, 2009, and a letter agreement (“Amendment No. 11”), dated as of November 16, 2009 (the Original Purchase Agreement, as amended, the “Purchase Agreement”), which provided for, among other things, Glencore AG’s purchase of up to US$50,000,000 in aggregate principal amount of floating rate secured debentures due September 30, 2011 issued by the Issuer Subsidiary (collectively, the “Debentures”).

The initial closing of the transactions contemplated by the Original Purchase Agreement occurred on October 31, 2008. At the initial closing, the Issuer Subsidiary issued to Glencore AG an initial tranche of US$7,500,000 of the Debentures (the “Tranche A Debenture”). Subsequently, the Issuer Subsidiary issued to Glencore AG a second tranche of US$7,500,000 of the Debentures (the “Tranche B Debenture”) on December 22, 2008, a third tranche of US$5,000,000 of the Debentures (the “Tranche C Debenture”) on June 17, 2009 and a fourth tranche of US$5,000,000 of the Debentures (the “Tranche D Debenture”) on August 31, 2009. The Original Purchase Agreement had also provided for a fifth tranche of US$25,000,000 of the Debentures (the “Tranche E Debenture”) to be issued to Glencore AG upon the satisfaction of additional closing conditions set forth in the Original Purchase Agreement.

The Tranche A Debenture, the Tranche B Debenture, the Tranche C Debenture and the Tranche D Debenture bear interest at a rate equal to the 12-month US dollar LIBOR plus 4%. Interest is payable in cash or by increasing the principal amount of such Debentures. On or before September 30, 2009, the Issuer was able to elect in which form to make the interest payments; thereafter, Glencore AG may make such election. As of June 30, 2013, approximately US$6,114,881.53 of interest had been added to the principal amount of such Debentures. The Issuer has guaranteed the Issuer Subsidiary’s obligations under such Debentures pursuant to a Parent Guarantee (the “Parent Guarantee”), dated as of October 31, 2008. The Issuer Subsidiary’s obligations under such Debentures are secured by (i) the assets of the Issuer pursuant to a security agreement (the “Issuer Security Agreement”), dated as of October 31, 2008, between the Issuer and Glencore AG, (ii) the assets of the Issuer Subsidiary pursuant to a security agreement (the “Issuer Subsidiary Security Agreement”), dated as of October 31, 2008, between the Issuer Subsidiary and Glencore AG, and (iii) a security interest in the Issuer’s equity interest in the Issuer Subsidiary pursuant to a pledge agreement (the “Pledge Agreement”), dated as of October 31, 2008, between the Issuer and Glencore AG.

In connection with the Original Purchase Agreement, on October 31, 2008, the Issuer issued to Glencore AG an exchange warrant pursuant to which the Debentures were exchangeable into Common Shares at any time at an exchange rate of US$4.00 per Common Share for the Tranche A Debenture, the Tranche B Debenture, the Tranche C Debenture and the Tranche D Debenture, and an exchange rate of US$2.65 per Common Share for the Tranche E Debenture (the “Original Exchange Warrant”).

In connection with the Original Purchase Agreement, on October 31, 2008, the Issuer issued to Glencore AG a purchase warrant entitling Glencore AG to purchase 6,250,000 Common Shares at an exercise price of US$3.00 per Common Share (the “2008 Purchase Warrant”).

Concurrently with the issuance of the Tranche A Debenture and the 2008 Purchase Warrant, the Issuer and Glencore AG entered into a Registration Rights Agreement (the “2008 Registration Rights Agreement”). The 2008 Registration Rights Agreement granted Glencore AG demand and piggyback registration rights with respect to Common Shares issuable upon exercise of the Original Exchange Warrant and/or exercise of the 2008 Purchase Warrant.

Pursuant to a subscription agreement, dated as of November 17, 2009, between Glencore AG and the Issuer (the “First 2009 Subscription Agreement”), Glencore AG acquired from the Issuer, on a private placement basis, 3,773,585 Common Shares for an aggregate purchase price of US$10,000,000.25 (or US$2.65 per Common Share). Pursuant to another subscription agreement, dated as of November 23, 2009, between Glencore AG and the Issuer (the “Second 2009 Subscription Agreement”), on January 26, 2010, Glencore AG acquired from the Issuer, on a private placement basis, 5,660,377 Common Shares for an aggregate purchase price of US$14,999,999.05 (or US$2.65 per Common Share).

On November 12, 2010, the Issuer, the Issuer Subsidiary and Glencore AG entered into an amendment and waiver agreement (the “2010 Amendment and Waiver”) pursuant to which the parties agreed, among other things, to:

On November 12, 2010, as contemplated by the 2010 Amendment and Waiver, the Issuer issued to Glencore AG a purchase warrant entitling Glencore AG to purchase 3,000,000 Common Shares at an exercise price of US$2.00 per Common Share until December 31, 2015 (the “2010 Purchase Warrant”).

In accordance with the terms of the 2010 Amendment and Waiver, the Issuer and Glencore AG also entered into a registration rights agreement, dated as of November 12, 2010 (the “2010 Registration Rights Agreement”), pursuant to which Glencore AG (and any transferee of Common Shares to whom Glencore AG transfers its registration rights) was granted demand and piggyback registration rights with respect to all Common Shares held by Glencore AG, including any Common Shares issuable upon exercise of the 2010 Purchase Warrant and/or exercise of the Original Exchange Warrant. The 2010 Registration Rights Agreement provides that the Issuer must effect an unlimited number of demand registration rights if holders of at least fifty percent (50%) of such registrable securities demand the registration of Common Shares covering at least twenty-five percent (25%) of the outstanding amount of such registrable securities (or a lesser percent if the anticipated aggregate offering price, net of underwriting discounts and commissions, would exceed US$5,000,000); provided, however, the Issuer is not obligated to effect (i) a registration covering the sale of Common Shares for an aggregate public offering price of less than US$5,000,000, (ii) more than two such registrations in any twelve-month period or (iii) any registration at a time when it is keeping three such registration statements effective.

Concurrently, Glencore AG and the Issuer entered into a Subscription Agreement, dated as of November 12, 2010 (the “2010 Subscription Agreement”), pursuant to which Glencore AG agreed to purchase from the Issuer, on a private placement basis, an aggregate of 15,000,000 Common Shares for a purchase price of US$2.00 per Common Share in three separate tranches of 5,000,000 Common Shares each.

On January 17, 2011, pursuant to the first tranche of the 2010 Subscription Agreement, Glencore AG acquired from the Issuer, on a private placement basis, 5,000,000 Common Shares for an aggregate purchase price of US$10,000,000 (or US$2.00 per Common Share).

The Issuer’s board of directors waived applicable provisions of the Issuer’s amended and restated shareholder rights plan agreement with respect to Glencore AG’s purchase of the remaining second and third tranches of the 2010 Subscription Agreement.

On July 15, 2011, pursuant to the second tranche of the 2010 Subscription Agreement, Glencore AG acquired an additional 5,000,000 Common Shares from the Issuer for an aggregate purchase price of US$10,000,000 (or US$2.00 per Common Share). Concurrently, Glencore AG granted a waiver to the Issuer pursuant to which Glencore AG waived the application of certain covenants contained in the Tranche A Debenture, the Tranche B Debenture, the Tranche C Debenture and the Tranche D Debenture to the secured loan provided by the Iron Range Resources and Rehabilitation Board to the Issuer Subsidiary that previously closed on June 28, 2011 (the “IRRRB Loan Waiver”).

On October 15, 2012, pursuant to the remaining third tranche of the 2010 Subscription Agreement, Glencore AG acquired an additional 5,000,000 Common Shares from the Issuer for an aggregate purchase price of US$10,000,000 (or US$2.00 per Common Share).

On July 15, 2011, Glencore AG acquired pursuant to a private transaction 9,200,547 Common Shares at a price of US$1.4233 per share. These shares were purchased from Cliffs Erie L.L.C. (“Cliffs”) in accordance with the Issuer’s right to arrange for a purchaser of the shares upon notice from Cliffs of its desire to sell the shares. The purchase was made pursuant to a share purchase agreement, which was previously filed with the SEC as an exhibit to the Statement, and is hereby incorporated herein by reference.

In connection with Glencore AG’s purchase from Cliffs, the Issuer’s board of directors waived applicable provisions of the Issuer’s amended and restated shareholder rights plan agreement with respect to Glencore AG becoming the beneficial owner of more than 20% of the outstanding voting shares of the Issuer as a result of the purchases described above.

On December 6, 2011, pursuant to a subscription agreement, dated as of November 30, 2011, between Glencore AG and the Issuer (the “2011 Subscription Agreement”), Glencore AG acquired from the Issuer, on a private placement basis, an aggregate of 13,333,333 Common Shares and a warrant entitling Glencore AG to purchase up to an aggregate of 2,600,000 Common Shares at an exercise price of US$1.50 per Common Share until December 31, 2015 (the “2011 Purchase Warrant”) for an aggregate purchase price of US$19,999,999.50.

In connection with the 2011 Subscription Agreement, on December 6, 2011, an amendment and waiver agreement, dated as of November 30, 2011, among the Issuer, the Issuer Subsidiary and Glencore AG (the “2011 Amendment and Waiver”), became effective and amended, among other things:

In addition, pursuant to the 2011 Amendment and Waiver, on December 6, 2011, the Issuer issued to Glencore AG an amended and restated exchange warrant that amended and restated the Original Exchange Warrant (the “Amended and Restated Exchange Warrant”). Pursuant to the Amended and Restated Exchange Warrant, the Tranche A Debenture, the Tranche B Debenture, the Tranche C Debenture and the Tranche D Debenture are exchangeable into Common Shares at an exchange rate of US$1.50 per Common Share for such Debentures at any time until the earlier of (i) the Issuer and/or the Issuer Subsidiary satisfying the Construction Prerequisites and (ii) September 30, 2014. The Amended and Restated Exchange Warrant further provides that the Issuer may, within 10 business days after the date on which the Issuer and/or the Issuer Subsidiary has satisfied the Construction Prerequisites, deliver a notice to Glencore AG requiring Glencore AG to exercise the Amended and Restated Exchange Warrant.

In addition, in connection with the 2011 Subscription Agreement and the 2011 Amendment and Waiver, on November 30, 2011, the Issuer and Glencore AG entered into a registration rights agreement and amendment to existing registration rights agreement (the “2011 Registration Rights Agreement”), pursuant to which (i) Glencore AG (and any transferee of Common Shares to whom Glencore AG transfers its registration rights) was granted demand and piggyback registration rights with respect to the Common Shares issued under the 2011 Subscription Agreement and the Common Shares issuable upon exercise of the 2011 Purchase Warrant and (ii) the 2010 Registration Rights Agreement was amended so that the registrable securities covered by the 2010 Registration Rights Agreement include the Common Shares issuable upon exercise of the 2010 Purchase Warrant, as amended by the 2011 Amendment and Waiver, and the Common Shares issuable upon exercise of the Amended and Restated Exchange Warrant.

The Issuer’s board of directors waived applicable provisions of the Issuer’s amended and restated shareholder rights plan agreement with respect to the transactions contemplated by the 2011 Subscription Agreement and the 2011 Amendment and Waiver.

On April 11, 2013, Glencore AG loaned US$20 million to the Issuer Subsidiary through the purchase of an amended Tranche E Debenture from the Issuer Subsidiary (as amended, the “Amended Tranche E Debenture”) pursuant to an amendment to the Purchase Agreement, dated as of April 10, 2013 (the “Amendment No. 14 to Purchase Agreement”), among the Issuer, the Issuer Subsidiary and Glencore AG. The Amended Tranche E Debenture had a maturity date of May 1, 2014, subject to mandatory repayment upon closing of the Rights Offering and carried a fixed interest rate of 4.721% per annum. Pursuant to a confirmation of secured obligations agreement (the “Confirmation of Secured Obligations Agreement”), dated as of April 10, 2013, among the Issuer Subsidiary, the Issuer and Glencore AG, the parties had confirmed that the Issuer Subsidiary’s obligations under the Amended Tranche E Debenture were guaranteed by the Issuer and secured by the assets of the Issuer and the Issuer Subsidiary on the same terms as the Tranche A Debenture, the Tranche B Debenture, the Tranche C Debenture and the Tranche D Debenture. On July 5, 2013, the Amended Tranche E Debenture was fully repaid with proceeds from the Rights Offering (as described below).

On July 5, 2013, at the closing of an offering of rights (“Rights”) by the Issuer to holders of Common Shares to raise up to approximately US$60.5 million in gross proceeds (the “Rights Offering”) contemplated by a standby purchase agreement, dated as of April 10, 2013, between Glencore AG and the Issuer (the “Standby Purchase Agreement”), Glencore AG acquired from the Issuer 31,756,979 Common Shares for an aggregate purchase price of US$20,959,606.14 (or US$0.66 per Common Share), of which 23,483,921 Common Shares were acquired by Glencore AG pursuant to the exercise of its basic subscription privilege under the Rights Offering and 8,273,058 Common Shares of which were acquired by Glencore AG pursuant to the exercise of its additional subscription privilege under the Rights Offering. In consideration for Glencore AG’s agreement to provide a standby commitment for the Rights Offering pursuant to the Standby Purchase Agreement, Glencore AG received a cash fee of approximately US$1.06 million at the closing of the Rights Offering. In addition, on July 5, 2013, at the closing of the Rights Offering, the Issuer and Glencore AG entered into (i) a corporate governance agreement (the “Corporate Governance Agreement”) under which, effective January 1, 2014, Glencore AG may appoint that number of the directors of the Issuer which is proportionate to Glencore AG’s ownership of Common Shares (on a fully diluted basis), subject to certain limitations including that Glencore AG may not appoint more than 49% (rounding down) of the Issuer’s directors and (ii) a registration rights agreement (the “2013 Registration Rights Agreement”) pursuant to which Glencore AG (and any transferee of Common Shares to whom Glencore AG transfers its registration rights) was granted demand and piggyback registration rights with respect to all Common Shares acquired by Glencore AG pursuant to the Rights Offering.

Glencore AG waived its right of first refusal on material financings by the Issuer contained in the 2010 Subscription Agreement with respect to the Rights Offering. In addition, the Issuer’s board of directors waived applicable provisions of the Issuer’s amended and restated shareholder rights plan agreement with respect to Glencore AG in connection with (i) the issuance of the Rights and Common Shares issuable upon exercise of the Rights under the Rights Offering and (ii) the Standby Purchase Agreement.

At the closing of the Rights Offering, as a result of the Rights Offering’s triggering of customary anti-dilution provisions: (i) the exchange rate at which the Tranche A Debenture, the Tranche B Debenture, the Tranche C Debenture and the Tranche D Debenture are exchangeable pursuant to the Amended and Restated Exchange Warrant was reduced from US$1.50 to US$1.29 per Common Share, (ii) the exercise prices for the 2010 Purchase Warrant and the 2011 Purchase Warrant were reduced from US$1.50 to US$1.30 per Common Share and (iii) the number of Common Shares issuable upon exercise of the 2010 Purchase Warrant and the 2011 Purchase Warrant were increased to 3,459,643 Common Shares and 2,998,358 Common Shares, respectively.

On April 25, 2014, the Issuer, the Issuer Subsidiary and Glencore AG entered into an amendment agreement (the “2014 Amendment”) pursuant to which the parties agreed, among other things, to:

The 2014 Amendment is subject to approval for the listing of additional shares from the NYSE MKT and the Toronto Stock Exchange.

The foregoing summaries of the Original Purchase Agreement, Amendment No. 1, Amendment No. 2, Amendment No. 3, Amendment No. 4, Amendment No. 5, Amendment No. 6, Amendment No. 7, Amendment No. 8, Amendment No. 9, Amendment No. 10, Amendment No. 11, the Tranche A Debenture, the Tranche B Debenture, the Tranche C Debenture, the Tranche D Debenture, the Parent Guarantee, the Issuer Security Agreement, the Issuer Subsidiary Security Agreement, the Pledge Agreement, the Original Exchange Warrant, the 2008 Purchase Warrant, the 2008 Registration Rights Agreement, the First 2009 Subscription Agreement, the Second 2009 Subscription Agreement, the 2010 Amendment and Waiver, the 2010 Purchase Warrant, the 2010 Registration Rights Agreement, the 2010 Subscription Agreement, the IRRRB Loan Waiver, the 2011 Subscription Agreement, the 2011 Purchase Warrant, the 2011 Amendment and Waiver, the Amended and Restated Exchange Warrant, the 2011 Registration Rights Agreement, the Amended Tranche E Debenture, the Amendment No. 14 to Purchase Agreement, the Confirmation of Secured Obligations Agreement, the Standby Purchase Agreement, the Corporate Governance Agreement and the 2013 Registration Rights Agreement do not purport to be complete and are qualified in their entirety by reference to the complete text of such agreements, which were previously filed with the SEC as exhibits to the Statement, and are hereby incorporated herein by reference. The foregoing summary of the 2014 Amendment does not purport to be complete and is qualified in its entirety by reference to the complete text of such agreement, which has been attached as Exhibit 99.44 to this Amendment No. 15 and is hereby incorporated herein by reference.

The source of funds for all of the purchases described above was working capital of the Reporting Persons. The Reporting Persons anticipate that the source of funds for any exercises of the 2010 Purchase Warrant and/or the 2011 Purchase Warrant will be working capital of the Reporting Persons.

Item 4. Purpose of Transaction

The Reporting Persons acquired the securities of the Issuer covered by this Schedule 13D for investment purposes. The Reporting Persons intend to continue to evaluate the Issuer’s business, financial condition, results of operations, capital structure, management, stock market performance, competitive outlook and other relevant factors. As part of such evaluations, the Reporting Persons may seek the views of, hold discussions with and respond to inquiries from representatives of the Issuer and other persons regarding the Issuer’s affairs. Depending on such evaluations, each Reporting Person may at any time and from time to time acquire Common Shares or securities convertible or exchangeable for Common Shares; dispose of Common Shares which it has acquired; and/or enter into privately negotiated derivative transactions with institutional counterparts to hedge the market risk of some or all of the positions in the Common Shares which it has acquired. Any acquisition or disposition of Common Shares by the Reporting Persons may be effected though open market or privately negotiated transactions, or otherwise. Any such transactions may be effected at any time and from time to time subject to any applicable limitations of the United States Securities Act of 1933, as amended. In the interest of maximizing shareholder value, the Reporting Persons may, from time to time, develop plans respecting, or propose changes in the management, policies, operations, capital structure or business of the Reporting Persons. Such plans or proposals may include or relate to one or more of the transactions specified in Items 4(a) through (j) of Schedule 13D under Rule 13d-1(a), including without limitation, a merger, disposition, sale of the Issuer’s assets or changes in the Issuer’s capitalization. Each Reporting Person reserves the right to change its plans and intentions at any time, as it deems appropriate.

Stephen Rowland, who is an employee of Glencore AG, is a member of the Issuer’s board of directors and currently serves on the Issuer’s audit and compensation committees. Pierre Vix, who is an employee of Glencore AG, is a member of the Issuer’s Technical Steering Committee.

As described in Item 3 of the Statement, on July 5, 2013, the Issuer and Glencore AG entered into the Corporate Governance Agreement under which, effective January 1, 2014, Glencore AG may appoint that number of the directors of the Issuer which is proportionate to Glencore AG’s ownership of Common Shares (on a fully diluted basis), subject to certain limitations including that Glencore AG may not appoint more than 49% (rounding down) of the Issuer’s directors.

Except as described herein, neither the Reporting Persons, nor, to the Reporting Persons’ knowledge, any of the Schedule 1 Persons has any present plans or proposals that relate to or would result in any of the actions described in Items 4(a) through (j) of Schedule 13D under Rule 13d-1(a). To the Reporting Persons’ knowledge, any of the Schedule 1 Persons may make the same evaluation and reserve the same rights.

Item 5. Interest in Securities of the Issuer

(a) and (b)

The Reporting Persons collectively own, directly or indirectly, 78,724,821 Common Shares. However, the Reporting Persons may be deemed to collectively have direct or indirect “beneficial ownership” within the meaning of Rule 13d-3 under the United States Securities Exchange Act of 1934, as amended (the “Exchange Act”), of (i) an additional 24,929,217 Common Shares issuable upon exercise of the Amended and Restated Exchange Warrant, (ii) an additional 3,459,643 Common Shares issuable upon exercise of the 2010 Purchase Warrant and (iii) an additional 2,998,358 Common Shares issuable upon exercise of the 2011 Purchase Warrant. Accordingly, each of the Reporting Persons may be deemed to beneficially own an aggregate of 110,112,039 Common Shares, representing 35.9% of the Issuer’s issued and outstanding Common Shares. This beneficial ownership percentage assumes that there are 307,037,610 Common Shares outstanding, which was calculated based on the sum of (i) 275,650,392 Common Shares outstanding on April 21, 2014 as reported by the Issuer in its Annual Report on Form 20-F for the fiscal year ended January 31, 2014 filed with the SEC on April 25, 2014, (ii) the 24,929,217 Common Shares issuable upon exercise of the Amended and Restated Exchange Warrant, (iii) the 3,459,643 Common Shares issuable upon exercise of the 2010 Purchase Warrant and (iv) the 2,998,358 Common Shares issuable upon exercise of the 2011 Purchase Warrant. The Reporting Persons share the power to vote or to direct the vote and dispose or to direct the disposition of the 110,112,039 Common Shares set forth above.

(c)            Except as set forth in Item 3 and this Item 5 of the Statement, none of the Reporting Persons nor, to the Reporting Persons’ knowledge, any of the Schedule 1 Persons, has beneficial ownership of any other Common Shares, or has engaged in any other transaction during the past 60 days in any Common Shares.

Mr. Stephen Rowland, who is a member of the Issuer’s board of directors and an employee of Glencore AG, owns 150,000 Common Shares and holds options to purchase 750,000 Common Shares.

Item 6 Contracts, Arrangements, Understandings or Relationships with Respect to Securities of the Issuer

Except as set forth in Item 3 of the Statement, to the best knowledge of the Reporting Persons, there are no other contracts, arrangements, understandings or relationships (legal or otherwise) among the persons named in Item 2 or between such persons and any other person with respect to any securities of the Issuer, including but not limited to, transfer or voting of any of the securities of the Issuer, joint ventures, loan or option arrangements, puts or calls, guarantees of profits, division of profits or loss, or the giving or withholding of proxies, or a pledge or contingency the occurrence of which would give another person voting power over the securities of the Issuer.

Item 7 Material to Be Filed as Exhibits

Signature

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

SCHEDULE 1

Set forth below are the names, business addresses and present principal occupations of the directors and executive officers of Glencore Xstrata plc, Glencore International AG and Glencore AG. Each executive officer of each of Glencore International AG and Glencore AG is also a director of such company. Where no business address is given for an executive officer or director, and such director’s principal employer is Glencore Xstrata plc or one of its subsidiaries, the business address is Baarermattstrasse 3, CH-6341, Baar, Switzerland. To the best knowledge of the Reporting Persons, none of the persons listed below beneficially owns any shares of Common Shares.

Directors of Glencore Xstrata plc:

Executive Officers of Glencore Xstrata plc:

Directors of Glencore International AG:

Directors of Glencore AG:

EXHIBIT 99.1

JOINT FILING AGREEMENT

Each of the undersigned hereby agrees that this Amendment No. 15 to the statement on Schedule 13D is being filed with the United States Securities and Exchange Commission on behalf of each of the undersigned pursuant to Rule 13d-1(k) under the United States Securities Exchange Act of 1934, as amended.

Dated: April 29, 2014

Exhibit 99.44

AMENDMENT

This Amendment Agreement (this “Agreement”), is made as of the 25th day of April 2014, by and among POLYMET MINING CORP., a corporation existing under the laws of British Columbia (the “Company”), POLY MET MINING, INC., a corporation existing under the laws of the State of Minnesota (the “Issuer”), and GLENCORE AG, a corporation existing under the laws of Switzerland (the “Purchaser”).

RECITALS

WHEREAS, the Company, the Issuer and the Purchaser are parties to that certain Purchase Agreement, dated as of October 31, 2008, as amended by Letter Agreement, dated November 28, 2008, as further amended by Amendment Letter No. 2, dated December 12, 2008, as further amended by Amendment Letter No. 3, dated December 19, 2008, as further amended by Amendment Letter No. 4, dated January 30, 2009, as further amended by Amendment Letter No. 5, dated February 24, 2009, as further amended by Amendment Letter No. 6, dated March 30, 2009, as further amended by Amendment Letter No. 7, dated April 28, 2009, as further amended by Amendment Letter No. 8, dated June 4, 2009, as further amended by Amendment Letter No. 9, dated August 31, 2009, as further amended by Amendment Letter No. 10, dated October 20, 2009, as further amended by Amendment Letter No. 11, dated November 16, 2009, as further amended by Amendment Letter No. 14, dated April 10, 2013, as further amended by the 2010 Amendment and Waiver (as defined below), and as further amended by the 2011 Amendment and Waiver (as defined below) (as amended, supplemented or otherwise modified from time to time, the “Purchase Agreement”);

WHEREAS, pursuant to the Purchase Agreement, among other things, (1) the Issuer agreed to issue Floating Rate Secured Debentures due September 30, 2011 (each, a “Debenture” and collectively, the “Debentures”) in five separate tranches, consisting of four Debentures in the aggregate principal amount of US$25,000,000 and a fifth Debenture in the principal amount of US$25,000,000 (the “Original Tranche E Debenture”), in each case to be issued and delivered by the Issuer and paid for by the Purchaser upon fulfillment or waiver of certain conditions set forth therein; and (2) the Company issued a warrant, exercisable from time to time (the “Exchange Warrant”), to purchase common shares of the Company, without par value (the “Common Shares”), in an amount equal to the principal amount of the Debentures divided by US$4.00;

WHEREAS, (1) the first Debenture in the original principal amount of US$7,500,000 (the “Tranche A Debenture”) was issued to the Purchaser on October 31, 2008; (2) the second Debenture in the original principal amount of US$7,500,000 (the “Tranche B Debenture”) was issued to the Purchaser on December 24, 2008; (3) the third Debenture in the original principal amount of US$5,000,000 (the “Tranche C Debenture”) was issued to the Purchaser on June 18, 2009; (4) the fourth Debenture in the original principal amount of US$5,000,000 (the “Tranche D Debenture” and together with the Tranche A Debenture, Tranche B Debenture and Tranche C Debenture, the “Outstanding Debentures”) was issued to the Purchaser on September 2, 2009; and (5) US$7,208,549 of interest has been capitalized as at the date hereof in connection with the Outstanding Debentures;

WHEREAS, the Company, the Issuer and the Purchaser entered into an Amendment and Waiver, dated as of November 12, 2010 (the “2010 Amendment and Waiver”), pursuant to which, among other things, (1) the maturity date of each of the Outstanding Debentures and the expiration date of the Exchange Warrant were extended from September 30, 2011 to September 30, 2012, and (2) any and all obligations of the Issuer to issue the Original Tranche E Debenture and any and all obligations of the Purchaser to purchase the Original Tranche E Debenture pursuant to the Purchase Agreement were terminated and discharged in all respects (the “Original Tranche E Debenture Termination”);

WHEREAS, the Company, the Issuer and the Purchaser entered into an Amendment and Waiver, dated as of November 30, 2011 (the “2011 Amendment and Waiver”), pursuant to which, among other things, the maturity date of each of the Outstanding Debentures was extended from September 30, 2012 to the earlier to occur of (i) the Company giving the Purchaser ten days notice that it has received permits necessary to start construction of the NorthMet project and availability of senior construction finance, in a form reasonably acceptable to the Purchaser (the “Early Maturity Event”), and (ii) September 30, 2014;

WHEREAS, on November 30, 2011, the Company and the Purchaser entered into an amendment to the Exchange Warrant (the “Amended and Restated Exchange Warrant”), pursuant to which (1) the expiration date of the Exchange Warrant was extended from September 30, 2012 to the earlier to occur of an Early Maturity Event and September 30, 2014, (2) the Exchange Warrant is exercisable to purchase Common Shares in an amount equal to the principal amount of the Outstanding Debentures plus accrued and unpaid interest thereon divided by US$1.50, and (3) upon the occurrence of an Early Maturity Event, the Purchaser will transfer the Outstanding Debentures to the Company in exchange for the issuance by the Company to the Purchaser of fully paid and non assessable Common Shares equal to the principal amount of the Outstanding Debentures plus accrued and unpaid interest thereon, divided by US$1.50.

WHEREAS, on April 10, 2013, the Company, the Issuer and the Purchaser rescinded the Original Tranche E Debenture Termination and amended the obligations of the Issuer pursuant to the Purchase Agreement to issue a fifth Debenture in the principal amount of US$20,000,000 (the “Amended Tranche E Debenture”);

WHEREAS, the Amended Tranche E Debenture matured on July 5, 2013 and the Company repaid all amounts outstanding under the Amended Tranche E Debenture with the proceeds the Company received from its US$60,500,000 rights offering to its shareholders completed on July 5, 2013 (the “Rights Offering”);

WHEREAS, on July 5, 2013, the exercise price of the Amended and Restated Exchange Warrant was adjusted to $1.2920 per share pursuant to the weighted-average anti-dilution adjustments set forth therein as a result of the closing of the Rights Offering; and

WHEREAS, the parties desire to amend and waive certain provisions of Outstanding Debentures and the Amended and Restated Exchange Warrant as set forth herein.

NOW THEREFORE, in consideration of the terms and conditions contained in this Agreement, and other good and valuable consideration, the receipt and sufficiency of which is hereby acknowledged, the parties, intending to be legally bound hereby, agree as follows:

Section 1. Definitions. Capitalized terms not defined in this Agreement shall have the meanings ascribed to such terms in the Purchase Agreement.

Section 2. Effectiveness. This Agreement shall become effective and be deemed effective as of the date hereof upon execution of counterparts of this Agreement by each of the Company, the Issuer and the Purchaser (the “Effective Date”); provided however that this Agreement is also subject to approval for the listing additional shares from the NYSE MKT and the Toronto Stock Exchange.

Section 3. Amendment to the Outstanding Debentures. From and after the Effective Date, the “Maturity Date” of each of the Tranche A Debenture, Tranche B Debenture, Tranche C Debenture and Tranche D Debenture will be extended to the earlier to occur of (a) an Early Maturity Event, and (b) September 30, 2015.

Section 4. Amendment to the Amended and Restated Exchange Warrant. From and after the Effective Date, the expiration date of the Exchange Warrant will be extended to the earlier to occur of (a) an Early Maturity Event, and (b) September 30, 2015.

Section 5. Representations and Warranties of the Company.

(a) Each of the Company and the Issuer hereby makes the following representations and warranties to the Purchaser:

(i) Authorization; Enforcement. Each of the Company and the Issuer has the requisite corporate power and authority to enter into and to consummate the transactions contemplated by this Agreement and otherwise to carry out its obligations hereunder. The execution and delivery of this Agreement by the Company and the Issuer and the consummation by the Company and the Issuer of the transactions contemplated hereby have been duly authorized by all necessary action on the part of the Company and the Issuer and no further action is required by the Company and the Issuer, their boards of directors or their shareholders in connection herewith. This Agreement has been duly executed by the Company and the Issuer and, when delivered in accordance with the terms hereof, will constitute the valid and binding obligation of the Company and the Issuer enforceable against the Company and the Issuer in accordance with its terms except (A) as limited by general equitable principles and applicable bankruptcy, insolvency, reorganization, moratorium and other laws of general application affecting enforcement of creditors’ rights generally, (B) as limited by laws relating to the availability of specific performance, injunctive relief or other equitable remedies, and (C) insofar as indemnification and contribution provisions may be limited by applicable law.

(b) The Purchaser hereby makes the following representations and warranties to the Company and the Issuer:

(i) Authorization; Enforcement. The Purchaser has the requisite corporate power and authority to enter into and to consummate the transactions contemplated by this Agreement and otherwise to carry out its obligations hereunder. The execution and delivery of this Agreement by the Purchaser and the consummation by the Purchaser of the transactions contemplated hereby have been duly authorized by all necessary action on the part of the Purchaser and no further action is required by the Purchaser, its board of directors or its shareholders in connection herewith. This Agreement has been duly executed by the Purchaser and, when delivered in accordance with the terms hereof, will constitute the valid and binding obligation of the Purchaser enforceable against the Purchaser in accordance with its terms except (A) as limited by general equitable principles and applicable bankruptcy, insolvency, reorganization, moratorium and other laws of general application affecting enforcement of creditors’ rights generally, (B) as limited by laws relating to the availability of specific performance, injunctive relief or other equitable remedies and (C) insofar as indemnification and contribution provisions may be limited by applicable law.

Section 6. Effect on Agreements. The foregoing amendments and agreements are given solely in respect of the transactions described herein. Except as expressly set forth herein, all of the terms and conditions of the Agreements (as defined the Purchase Agreement) shall continue in full force and effect after the execution of this Agreement, and shall not be in any way changed, modified or superseded by the terms set forth herein.

Section 7. Filing of Form 6-K. The Company shall promptly upon receipt of a fully executed copy of this Agreement, file a Report of Foreign Private Issuer on Form 6-K disclosing all material aspects of the transactions contemplated hereby.

Section 8. Amendments and Waivers. The provisions of this Agreement, including the provisions of this sentence, may not be amended, modified or supplemented, and waivers or consents to departures from the provisions hereof may not be given, unless the same shall be in writing and signed by the Company, the Issuer and the Purchaser.

Section 9. Notices. Any and all notices or other communications or deliveries required or permitted to be provided hereunder shall be delivered as set forth in the applicable Agreement (as defined in the Purchase Agreement).

Section 10. Successors and Assigns. This Agreement may not be assigned by any party with the prior written consent of the other parties. The terms and conditions of this Agreement shall inure to the benefit of and be binding upon the respective permitted successors and assigns of the parties. Nothing in this Agreement, express or implied, is intended to confer upon any party other than the parties hereto or their respective successors and assigns any rights, remedies, obligations, or liabilities under or by reason of this Agreement, except as expressly provided in this Agreement.

Section 11. Execution and Counterparts. This Agreement may be executed in two or more counterparts, all of which when taken together shall be considered one and the same agreement. In the event that any signature is delivered by facsimile transmission or by e-mail delivery of a “.pdf” format data file, such signature shall create a valid and binding obligation of the party executing (or on whose behalf such signature is executed) with the same force and effect as if such facsimile or “.pdf” signature page were an original thereof.

Section 12. Expenses. The parties hereto shall each pay the legal fees and disbursements of their respective legal counsel in connection with the preparation, negotiation, execution and delivery of this Agreement.

Section 13. Further Assurances. The parties shall execute and deliver all such further instruments and documents and take all such other actions as may reasonably be required to carry out the transactions contemplated hereby and to evidence the fulfillment of the agreements herein contained.

Section 14. Governing Law. All questions concerning the construction, validity, enforcement and interpretation of this Agreement shall be determined in accordance with the Sections 2.8 of the Purchase Agreement.

Section 15. Consent to Jurisdiction. The parties consent to the jurisdiction and venue set forth in Section 11.11 of the Purchase Agreement.

Section 16. Severability. If one or more provisions of this Agreement are held to be unenforceable under Applicable Law, such provision shall be excluded from this Agreement and the balance of this Agreement shall be interpreted as if such provision were so excluded and shall be enforceable in accordance with its terms.

Section 17. Headings. The headings in this Agreement are for convenience only, do not constitute a part of the Agreement and shall not be deemed to limit or affect any of the provisions hereof.

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IN WITNESS WHEREOF, the parties have duly executed this Amendment as of the date first written above.