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                                                                    EXHIBIT 10.1


                          FIRST SUPPLEMENTAL INDENTURE

                          dated as of December 20, 2005

                                       to

                                    INDENTURE

                          dated as of November 28, 2001

                                      among



                          COMPASS MINERALS GROUP, INC.,

                                   as Issuer,

                          the Guarantors named herein,



                                       and

                    The Bank of New York Trust Company, N.A.,

                                   as Trustee





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         THIS FIRST SUPPLEMENTAL INDENTURE to the Indenture (as defined below)
(the "First Supplemental Indenture"), dated as of December 20, 2005, is made
among COMPASS MINERALS GROUP, INC., a Delaware corporation (the "Company"),
CAREY SALT COMPANY, a Delaware corporation, GREAT SALT LAKE MINERALS
CORPORATION, a Delaware corporation, GSL CORPORATION, a Delaware corporation,
NAMSCO INC., a Delaware corporation, and NORTH AMERICAN SALT COMPANY, a Delaware
corporation, as guarantors (collectively, the "Guarantors"), and THE BANK OF NEW
YORK TRUST COMPANY, as successor Trustee (the "Trustee"), and amends the
Indenture, dated as of November 28, 2001, among the Company, the Guarantors and
The Bank of New York, Trustee (as amended from time to time, the "Indenture").

                                    RECITALS:

         A. Pursuant to the Indenture, the Company has issued its 10% Senior
Subordinated Notes due 2011 (the "Notes").

         B. The Company, the Guarantors and the Trustee desire by this First
Supplemental Indenture to amend certain provisions of the Indenture.

         C. Consent to the amendments set forth in Article I herein have been
received from the Holders of more than a majority in principal amount of the
outstanding Notes.

         D. Capitalized terms used herein without definition shall have the
meanings assigned to them in the Indenture.

         E. The recitals set forth above shall be deemed to be statements by the
Company and the Guarantors, and not statements by the Trustee.

         NOW, THEREFORE, it is hereby agreed as follows:

                                    ARTICLE I
                                   AMENDMENTS

         SECTION 1.01. Certain Defined Terms. The following provisions set forth
in Section 1.1 (Definitions) of the Indenture are hereby amended as follows:

         (a) The definition of each of "Acquired Indebtedness", "Affiliate
Transaction", "Asset Acquisition", "Capitalized Lease Obligation", "Commodity
Agreement", "Consolidated EBITDA", "Consolidated Fixed Charge Coverage Ratio",
"Consolidated Fixed Charges", "Consolidated Interest Expense", "Consolidated Net
Income", "Consolidated Non-cash Charges", "Excluded Contribution", "Net Proceeds
Offer", "Net Proceeds Offer Amount", "Net Proceeds Offer Payment Date", "Net
Proceeds Offer Trigger Date", "New Domestic Restricted Subsidiary", "Permitted
Business", "Permitted Indebtedness", "Permitted Investments", "Permitted Liens",
Purchase Money Indebtedness", "Qualified Receivables Transaction", "Receivables
Subsidiary", "Refinancing Indebtedness", "Replacement Assets", "Restricted
Payment", and "Transaction Date" is deleted in its entirety.


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         (b) Subsection (2) of the definition of "Guarantor" is deleted in its
entirety and replaced with the following:

                       "(2) {Reserved}".

         (c) The following language is hereby deleted from the definition of
"Indebtedness":

         "For purposes of Section 4.4, in determining the principal amount of
         any Indebtedness to be incurred by the Company or any Restricted
         Subsidiary or which is outstanding at any date, the principal amount of
         any Indebtedness which provides that an amount less than the principal
         amount thereof shall be due upon any declaration of acceleration
         thereof shall be the accreted value thereof at the date of
         determination."

         (d) Subsection (6) of the definition of "Guarantor Senior Debt" is
deleted in its entirety and replaced with the following:

                       "(6) {Reserved}".

         (e) The following language is hereby deleted from the definition of
"Investment":

                       "For purposes of Section 4.3:

                                (1) "Investment" shall include and be valued at
             the fair market value of the net assets of any Restricted
             Subsidiary of the Company at the time that such Restricted
             Subsidiary is designated an Unrestricted Subsidiary of the Company
             and shall exclude the fair market value of the net assets of any
             Unrestricted Subsidiary of the Company at the time that such
             Unrestricted Subsidiary is designated a Restricted Subsidiary of
             the Company; and

                                (2) the amount of any Investment shall be the
             original cost of such Investment plus the cost of all additional
             Investments by the Company or any of its Restricted Subsidiaries,
             without any adjustments for increases or decreases in value, or
             write-ups, write-downs or write-offs with respect to such
             Investments, reduced by the payment of dividends or distributions
             in connection with such Investment or any other amounts received in
             respect of such Investment; provided that no such payment of
             dividends or distributions or receipt of such other amounts shall
             reduce the amount of any Investment if such payment of dividends or
             distributions or receipt of any such amounts would be included in
             Consolidated Net Income.

                       If the Company or any Restricted Subsidiary of the
         Company sells or otherwise disposes of any Common Stock of any Person
         that prior to such sale or disposition was a direct or indirect
         Restricted Subsidiary of the Company and after giving effect to any
         such sale or disposition, ceases to be a Restricted Subsidiary of the
         Company, the Company shall be deemed to have made an investment on the
         date of any such sale or disposition equal to the fair market value of
         the Common Stock of such Person not sold or disposed of."


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         (f) Subsection (6) of the definition of "Senior Debt" is deleted in its
entirety and replaced with the following:

                       "(6) {Reserved}".

         (g) The definition of "Unrestricted Subsidiary" is deleted in its
entirety and replaced with the following:

                       ""Unrestricted Subsidiary" of any Person means (1) any
         Subsidiary of such Person that at the time of determination shall be or
         continue to be designated an Unrestricted Subsidiary by the Board of
         Directors of such Person in the manner provided below and (2) any
         Subsidiary of an Unrestricted Subsidiary. The Board of Directors may
         designate any Subsidiary (including any newly acquired or newly formed
         Subsidiary) to be an Unrestricted Subsidiary unless such Subsidiary
         owns any Capital Stock of, or owns or holds any Lien on any property
         of, the Company or any other Subsidiary of the Company that is not a
         Subsidiary of the Subsidiary to be so designated; provided that (x) the
         Subsidiary to be so designated at the time of designation has total
         consolidated assets of $1,000 or less and (y) each Subsidiary to be so
         designated and each of its Subsidiaries has not at the time of
         designation, and does not thereafter, create, incur, issue, assume,
         guarantee or otherwise become directly or indirectly liable with
         respect to any Indebtedness pursuant to which the lender has recourse
         to any of the assets of the Company or any of its Restricted
         Subsidiaries (other than the assets of such Unrestricted Subsidiary).
         The Board of Directors may designate any Unrestricted Subsidiary to be
         a Restricted Subsidiary only if immediately before and immediately
         after giving effect to such designation, no Default or Event of Default
         shall have occurred and be continuing. Any such designation by the
         Board of Directors shall be evidenced to the Trustee by promptly filing
         with the Trustee a copy of the Board Resolution giving effect to such
         designation and an Officers' Certificate certifying that such
         designation complied with the foregoing provisions."

         SECTION 1.02. The fourth paragraph of Section 2.2 (Execution and
Authentication) is hereby deleted in its entirety and replaced with the
following:

                       "The Trustee shall authenticate (i) Initial Notes for
         original issue on the Issue Date in the aggregate principal amount not
         to exceed $250,000,000, (ii) pursuant to the Exchange Offer, Exchange
         Notes from time to time for issue only in exchange for a like principal
         amount of Initial Notes and (iii) one or more series of Securities for
         original issue after the Issue Date (such Securities to be
         substantially in the form of Exhibit A or B, as the case may be) in an
         unlimited amount (and if in the form of Exhibit A the same principal
         amount of Exchange Notes in exchange therefor upon consummation of a
         registered exchange offer), in each case upon written orders of the
         Issuer in the form of an Officers' Certificate. In addition, each such
         Officers' Certificate shall specify the amount of Securities to be
         authenticated, the date on which the Securities are to be
         authenticated, whether the Securities are to be Initial Notes, Exchange
         Notes or Securities issued under clause (iii) of the preceding sentence
         and the aggregate principal amount of Securities outstanding on the
         date of authentication, and shall further specify the amount of such
         Securities to be issued as a Global Security or


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         Physical Securities. Such Securities shall initially be in the form of
         one or more Global Securities, which (i) shall represent, and shall be
         denominated in an amount equal to the aggregate principal amount of,
         the Securities to be issued, (ii) shall be registered in the name of
         the Depository for such Global Security or Securities or its nominee
         and (iii) shall be delivered by the Trustee to the Depository or
         pursuant to the Depository's instruction. All Securities issued under
         this Indenture shall vote and consent together on all matters as one
         class and no series of Securities will have the right to vote or
         consent as a separate class on any matter.".

         SECTION 1.03. The third sentence of Section 2.3 ("Registrar and Paying
Agent") is hereby deleted in its entirety and replaced with the following:

                       "The Issuer may act as its own Registrar or Paying Agent
         except that, for the purposes of Articles Three and Eight and Section
         4.17, neither the Issuer nor any Affiliate of the Issuer shall act as
         Paying Agent."

         SECTION 1.04. The following language in subsection (a) of Section 2.6
("Transfer and Exchange") is hereby deleted:

                       "4.18".

         SECTION 1.05. Subsection (b) of Section 4.8 (Compliance Certificate;
Notice of Default) is hereby deleted in its entirety and replaced with the
following:

                       "(b) {Reserved}".

         SECTION 1.06. The heading and text of each of Section 4.3 (Limitation
On Restricted Payments), Section 4.4 (Limitation on Incurrence of Additional
Indebtedness), Section 4.6 (Payment of Taxes and Other Claims), Section 4.7
(Maintenance of Properties and Insurance), Section 4.9 (Compliance With Laws),
Section 4.10 (Reports To Holders), Section 4.11 (Waiver of Stay, Extension or
Usury Laws), Section 4.12 (Limitation on Transactions with Affiliates), Section
4.13 (Limitation on Dividend and Other Payment Restrictions Affecting
Subsidiaries), Section 4.14 (Limitation on the Issuance and Sale of Capital
Stock of Restricted Subsidiaries), Section 4.15 (Limitation on Issuances of
Guarantees by Restricted Subsidiaries), Section 4.16 (Limitation on Liens),
Section 4.18 (Limitation on Asset Sales), Section 4.19 (Prohibition on
Incurrence of Senior Subordinated Debt), Section 4.20 (Future Guarantors),
clauses (ii)-(iv) of Section 5.1(a) (Merger, Consolidation and Sale of Assets),
and clauses (iii)-(v) of Section 6.1 (Events of Default) of the Indenture are
deleted in their entirety and replaced with the following:

                       "{Reserved}".

         SECTION 1.07. Any Notes issued under any provision of the Indenture
subsequent to the date of this First Supplemental Indenture shall bear a
notation, in form acceptable to the Trustee, referring to this First
Supplemental Indenture, and shall vary from the form attached to the Indenture
as Exhibit A as follows:


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         (a) Section 4 of the form of Note attached as Exhibit A to the
Indenture shall be deleted in its entirety and replaced with the following:

                       "Indenture. The Issuer issued the Securities under an
         Indenture dated as of November 28, 2001 (as amended pursuant to the
         First Supplemental Indenture dated as of December 20, 2005 among the
         Company, the Guarantors party thereto and the Trustee, the "Indenture")
         among the Company, the Guarantors and the Trustee. This Security is one
         of a duly authorized issue of Securities of the Issuer. Capitalized
         terms herein are used as defined in the Indenture unless otherwise
         defined herein. The terms of the Securities include those stated in the
         Indenture and those made part of the Indenture by reference to the
         Trust Indenture Act of 1939 (15 U.S.C. (S)(S) 77aaa-77bbbb) (the
         "TIA"), as in effect on the date of the Indenture until such time as
         the Indenture is qualified under the TIA, and thereafter as in effect
         on the date on which the Indenture is qualified under the TIA.
         Notwithstanding anything to the contrary herein, the Securities are
         subject to all such terms, and Holders of Securities are referred to
         the Indenture and the TIA for a statement of them. The Securities are
         general obligations of the Issuer unlimited in amount.".

         (b) The text of each of Sections 9 and 16 of the form of Note attached
as Exhibit A to the Indenture shall be deleted in its entirety and replaced with
the following:

         "{Reserved}".

         (c) The "Option of Holder to Elect Purchase" form attached to the form
of Note attached as Exhibit A to the Indenture shall be amended to delete the
following:

         "or Section 4.18" and "Section 4.18".

                                   ARTICLE II
                                  MISCELLANEOUS

         SECTION 2.01. Effectiveness. This First Supplemental Indenture will
become effective upon the execution and delivery of the First Supplemental
Indenture by the parties hereto provided that the amendments to the Indenture
set forth in Article I above shall not become operative unless and until Notes
are accepted for payment by the Company pursuant to its Offer to Purchase and
Consent Solicitation Statement dated November 21, 2005.

         SECTION 2.02. Confirmation. This First Supplemental Indenture and the
Indenture shall henceforth be read together. Except as expressly set forth
herein, the Indenture shall remain unchanged and is in all respects confirmed
and preserved.

         SECTION 2.03. Counterparts. This First Supplemental Indenture may be
executed in counterparts, each of which shall be deemed an original, but all of
which together shall constitute one instrument.

         SECTION 2.04. Governing Law. This First Supplemental Indenture shall be
governed by and construed in accordance with the laws of the State of New York,
but without giving effect to


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applicable principles of conflicts of law to the extent that the application of
the law of another jurisdiction would be required thereby.

         SECTION 2.05. Trustee. The Trustee makes no representations as to the
validity or sufficiency of this First Supplemental Indenture. The recitals and
statements herein are deemed to be those of the Issuer and Guarantors and not of
the Trustee.






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         IN WITNESS WHEREOF, the parties hereto caused this First Supplemental
Indenture to be duly executed as of the date first written above.

                                         COMPASS MINERALS GROUP, INC.

                                         By: /s/ Rodney L. Underdown
                                            ------------------------------------
                                            Rodney L. Underdown
                                            Vice President and Chief Financial
                                            Officer; Secretary

                                         CAREY SALT COMPANY
                                         GREAT SALT LAKE MINERALS CORPORATION
                                         GSL CORPORATION
                                         NAMSCO INC.
                                         NORTH AMERICAN SALT COMPANY
                                         as Guarantors

                                         By: /s/ Rodney L. Underdown
                                            ------------------------------------
                                            Rodney L. Underdown
                                            Authorized Representative



                                         THE BANK OF NEW YORK TRUST COMPANY,
                                         N.A., AS TRUSTEE

                                         By: /s/ Roxane Ellwanger
                                            ------------------------------------
                                         Name:   Roxane Ellwanger
                                              ----------------------------------
                                         Title:  Assistant Vice President
                                               ---------------------------------