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                                                                      EXHIBIT 31

                                  CERTIFICATION

            PURSUANT TO SECTION 302 OF THE SARBANES-OXLEY ACT OF 2002

I, A. Terrance MacGibbon, certify that:

      1.    I have reviewed this annual report on Form 40-F of FNX Mining
            Company Inc.;

      2.    Based on my knowledge, this annual report does not contain any
            untrue statement of a material fact or omit to state a material fact
            necessary to make the statements made, in light of the circumstances
            under which such statements were made, not misleading with respect
            to the period covered by this annual report;

      3.    Based on my knowledge, the financial statements, and other financial
            information included in this annual report, fairly present in all
            material respects the financial condition, results of operations and
            cash flows of the registrant as of, and for, the periods presented
            in this annual report;

      4.    The registrant's other certifying officer and I are responsible for
            establishing and maintaining disclosure controls and procedures (as
            defined in Exchange Act Rules 13a-15(e) and 15d-15(e) for the
            registrant and have:

                  a.    Designed such disclosure controls and procedures, or
                        caused such disclosure controls and procedures to be
                        designed under our supervision, to ensure that material
                        information relating to the registrant, including its
                        consolidated subsidiaries, is made known to us by others
                        within those entities, particularly during the period in
                        which this annual report is being prepared;

                  b.    Evaluated the effectiveness of the registrant's
                        disclosure controls and procedures and presented in this
                        report our conclusions about the effectiveness of the
                        disclosure controls and procedures, as of the end of the
                        period covered by this report based on such evaluation;
                        and

                  c.    Disclosed in this report any change in the registrant's
                        internal control over financial reporting that occurred
                        during the period covered by the annual report that has
                        materially affected, or is reasonably likely to
                        materially affect, the registrant's internal control
                        over financial reporting; and

      5.    The registrant's other certifying officer and I have disclosed,
            based on our most recent evaluation of internal control over
            financial reporting, to the registrant's auditors and the audit
            committee of registrant's board of directors (or persons performing
            the equivalent function):

                  a.    All significant deficiencies and material weaknesses in
                        the design or operation of internal control over
                        financial reporting which are reasonably likely to
                        adversely affect the issuer's ability to record,
                        process, summarize and report financial information; and

                  b.    Any fraud, whether or not material, that involves
                        management or other employees who have a significant
                        role in the issuer's internal control over financial
                        reporting.

Date: March 31, 2005            /s/ T. MacGibbon
                                --------------------------------------------
                                By:    A. Terrance MacGibbon
                                Title: President and Chief Executive Officer

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I, John Ross, certify that:

      1.    I have reviewed this annual report on Form 40-F of FNX Mining
            Company Inc.;

      2.    Based on my knowledge, this annual report does not contain any
            untrue statement of a material fact or omit to state a material fact
            necessary to make the statements made, in light of the circumstances
            under which such statements were made, not misleading with respect
            to the period covered by this annual report;

      3.    Based on my knowledge, the financial statements, and other financial
            information included in this annual report, fairly present in all
            material respects the financial condition, results of operations and
            cash flows of the registrant as of, and for, the periods presented
            in this annual report;

      4.    The registrant's other certifying officer and I are responsible for
            establishing and maintaining disclosure controls and procedures (as
            defined in Exchange Act Rules 13a-15(e) and 15d-15(e) for the
            registrant and have:

                  a.    Designed such disclosure controls and procedures, or
                        caused such disclosure controls and procedures to be
                        designed under our supervision, to ensure that material
                        information relating to the registrant, including its
                        consolidated subsidiaries, is made known to us by others
                        within those entities, particularly during the period in
                        which this annual report is being prepared;

                  b.    Evaluated the effectiveness of the registrant's
                        disclosure controls and procedures and presented in this
                        report our conclusions about the effectiveness of the
                        disclosure controls and procedures, as of the end of the
                        period covered by this report based on such evaluation;
                        and

                  c.    Disclosed in this report any change in the registrant's
                        internal control over financial reporting that occurred
                        during the period covered by the annual report that has
                        materially affected, or is reasonably likely to
                        materially affect, the registrant's internal control
                        over financial reporting; and

      5.    The registrant's other certifying officer and I have disclosed,
            based on our most recent evaluation of internal control over
            financial reporting, to the registrant's auditors and the audit
            committee of registrant's board of directors (or persons performing
            the equivalent function):

                  a.    All significant deficiencies and material weaknesses in
                        the design or operation of internal control over
                        financial reporting which are reasonably likely to
                        adversely affect the issuer's ability to record,
                        process, summarize and report financial information; and

                  b.    Any fraud, whether or not material, that involves
                        management or other employees who have a significant
                        role in the issuer's internal control over financial
                        reporting.

Date: March 31, 2005                       /s/ J. Ross
                                           ----------------------------------
                                               By:    John Ross
                                               Title: Chief Financial Officer