GLENCORE AG December 19, 2008

Exhibit 99.13

GLENCORE AG

December 19, 2008

Xxxxxxx Xxxxx

Poly Met Mining Inc.

0000 Xxxxxxx Xxxx 000

Xxxx Xxxxx, Xxxxxxxxx

Re: Amendment Letter No. 3 Relating to Purchase Agreement

Dear Xxxxxxx,

Reference is made to the Purchase Agreement dated October 31, 2008 by and among the Poly Met Mining Inc., as issuer (the “Issuer”), PolyMet Mining Corp., as parent guarantor (the “Company”), and Glencore AG, as purchaser (the “Purchaser”), as amended by letter agreement dated November 28, 2008, and as further amended by Amendment Letter No. 2 dated December 12, 2008 (as amended, supplemented or otherwise modified from time to time, the “Purchase Agreement”). Capitalized terms used herein and not otherwise defined shall have the meanings set forth in the Purchase Agreement.

The Purchaser hereby agrees to extend the date by which the Issuer shall have delivered to the Purchaser the executed consent to the Erie Plant Mortgage (the “Executed Consent”), as set forth in Section 4.8(b) of the Purchase Agreement, to Friday, January 30, 2009 (the “New Due Date”).

In addition, the Purchaser hereby further agrees to permit the Issuer to deliver the documents and agreements described in subclauses (d), (e) and (f) (solely as such subclause relates to the Erie Plant Mortgage and the Erie Plant Mortgage Amendment) of Section 4.4 of the Purchase Agreement on or before the New Due Date (collectively, the “Erie Plant Mortgage Documents”) as conditions subsequent to the Tranche B Closing.

The New Due Date shall be inclusive of any applicable cure or notice period, and the failure to provide the Purchaser with the Executed Consent and the Erie Plant Mortgage Documents on or before the New Due Date shall be a failure by the Issuer and the Company to comply with their covenants under the Purchase Agreement, and shall result in, among other things, the failure to satisfy the conditions to the Tranche B Closing, the occurrence of an Event of Default under the Tranche B Debenture and the occurrence of an Event of Default under the Tranche A Debenture.

Xxxxxxxxxxxxxxxxx 0 % X.X. Xxx 000 % XX-0000 Xxxx % Switzerland

Telephone x00 00 000 00 00 % Telefax x00 00 000 00 00

GLENCORE Page  2

Except as specifically amended hereby, the Purchase Agreement shall remain in full force and effect.

Best regards,
/s/ Xxxxxx Xxxxxxxx		/s/ Xxxxxx Xxxxxx
Xxxxxx Xxxxxxxx Officer		Xxxxxx Xxxxxx Officer
GLENCORE AG

ACKNOWLEDGED AND AGREED TO THIS 19th DAY OF DECEMBER, 2008:
POLY MET MINING INC.
By:		/s/ Xxxxxxx Xxxxx
Name:		Xxxxxxx Xxxxx
Title:		Chief Financial Officer
POLYMET MINING CORP.
By:		/s/ Xxxxxxx Xxxxx
Name:		Xxxxxxx Xxxxx
Title:		Chief Financial Officer