Document:

<PAGE>
                                                                   EXHIBIT 10(U)

                               FOURTH AMENDMENT TO
                AMENDED AND RESTATED LOAN AND SECURITY AGREEMENT

         This Fourth Amendment to Amended and Restated Loan and Security
Agreement (this "Fourth Amendment") dated as of December 31, 2001 by and among
United States Lime & Minerals, Inc., a Texas corporation ("U.S. Lime"), Texas
Lime Company, a Texas corporation ("TLC"), and Arkansas Lime Company, an
Arkansas corporation ("ALC," and together with U.S. Lime and TLC, collectively
referred to as the "Borrowers" and individually as a "Borrower"), and First
Union National Bank, a national banking association, as successor to CoreStates
Bank, N.A. ("Bank").
                                   BACKGROUND

         A. Borrowers and Bank are parties to an Amended and Restated Loan and
Security Agreement dated December 30, 1997, as amended by the First Amendment to
Amended and Restated Loan and Security Agreement, the Second Amendment to
Amended and Restated Loan and Security Agreement, a letter agreement dated as of
April 21, 2000, and the Third Amendment to Amended and Restated Loan and
Security Agreement dated as of April 26, 2001 (as the same has been amended and
may hereafter amended, restated, supplemented or otherwise modified and in
effect from time to time, the "Loan Agreement"), pursuant to which Bank
continued and restated certain credit facilities for the benefit of Borrowers
under the terms and conditions set forth therein. All initially capitalized
terms used in this Fourth Amendment, unless otherwise specifically defined
herein, shall have the meanings ascribed to them in the Loan Agreement.

         B. Bank and Borrowers desire to further amend the Loan Agreement to
temporarily permit Borrowers to request Cash Advances which exceed the Borrowing
Base by up to $750,000 according to the terms hereof.

         NOW, THEREFORE, in consideration of the foregoing and of the mutual
covenants set forth herein, the parties hereto, intending to be legally bound
hereby, agree as follows:

                  1. Ratification. This Fourth Amendment is a modification of
the Loan Agreement pursuant to Section 9.2 thereof. Except as expressly set
forth herein, or in any amendment to any of the documents referred to herein,
Borrowers and Bank acknowledge and agree that each and every term, condition and
provision of the Loan Agreement is hereby ratified and confirmed in full.

                  2. Overadvances Temporarily Permitted.

                           2.1 Notwithstanding the Borrowing Base limitation for
Cash Advances under Section 2.2.1 of the Loan Agreement, for the period
commencing on and after the date hereof

<PAGE>

and expiring on July 31, 2002 (the "Overadvance Period"), Borrowers may request
Cash Advances in amounts not to exceed the lesser of (a) $5,000,000, or (b) the
sum of (i) the then available Borrowing Base, and (ii) the lesser of (A)
$750,000, or (B) the difference between the then available Borrowing Base and
the Overadvance Borrowing Base.

                           2.2 "Overadvance Borrowing Base" means the sum of (i)
100% of Borrowers' Eligible Accounts; plus (ii) the lesser of $1,000,000 and
100% of Eligible Inventory; less (a) the aggregate amount of all outstanding
Cash Advances, and (b) the face amount of all issued and outstanding Letters of
Credit.

         3. Revolving Credit Termination Date Extended. The defined term
"Revolving Credit Termination Date" is hereby amended and restated in its
entirety as of the date hereof as follows:

                  "Revolving Credit Termination Date" means July 31, 2002, or
                  such later date as Borrowers and Bank may agree in writing.

         4. Outstanding Indebtedness. Borrowers hereby unconditionally
acknowledge that, as of the date hereof, the outstanding principal balance under
the Revolving Credit is $2,325,000, and the aggregate face amount of outstanding
undrawn Letters of Credit is $133,000. Borrowers acknowledge and agree that the
foregoing balance of the Revolving Credit (including the amount of all draws
under outstanding Letters of Credit), together with interest, which shall accrue
from the date hereof at the rates set forth in the Loan Agreement, is owing to
Bank without claim, counterclaim, recoupment, defense or setoff of any kind.

         5. Representations and Warranties. To induce Bank to enter into this
Fourth Amendment, Borrowers jointly and severally represent and warrant to Bank
as follows:

                  5.1 After giving effect to the modifications contained herein,
all representations, warranties and covenants made by Borrowers to Bank in the
Loan Agreement (except those relating to a specific date) are true and correct
in all material respects as of the date hereof, with the same force and effect
as though made as of the date hereof;

                  5.2 No Event of Default or Unmatured Event of Default has
occurred and is continuing under the Loan Agreement as of the date hereof;

                  5.3 Each Borrower is a corporation validly subsisting under
the laws of the state of its incorporation; the execution, delivery and
performance of this Fourth Amendment and any other documents and instruments
executed and delivered to Bank in connection herewith (i) are within each
Borrower's corporate powers, (ii) have been duly authorized by each Borrower's
Board of Directors, (iii) do not contravene any provision of law or any
indenture, agreement or undertaking to which any Borrower is a party or is
otherwise bound, any Borrower's Certificate of Incorporation,

                                       2
<PAGE>

bylaws, or any resolution of the Board of Directors of any Borrower, and (iv)
require no consent or approval of any governmental authority or any fourth
party; and

                  5.4 This Fourth Amendment and any other documents and
instruments executed and delivered to Bank in connection herewith have been
validly executed and are enforceable against the Borrower or Borrowers party
thereto in accordance with their respective terms.

Any failure of any of the representations and warranties made by Borrowers in
this Fourth Amendment to be true and correct in all material respects when made
shall constitute an Event of Default under the Loan Agreement.

         6. Conditions Precedent. The effectiveness of this Fourth Amendment,
and the performance by Bank of its obligations described herein, are subject to
the conditions precedent that Bank shall have received, in form and substance
satisfactory to Bank:

                  6.1 resolutions of the Boards of Directors of each Borrower
authorizing the execution, delivery and performance of this Fourth Amendment and
the other documents and instruments executed and delivered to Bank in connection
herewith, certified by such Borrower's Secretary that the same are true and
complete copies of the originals thereof and remain in full force and effect,
not having been modified or rescinded;

                  6.2 a completed and executed Borrowing Base Certificate for
the month ended November 30, 2001; and

                  6.3 an amendment fee payable to Bank equal to $6,250.

         7. Miscellaneous.

                  7.1 Entire Agreement. The Loan Agreement, as amended by this
Fourth Amendment, and the other Loan Documents, embody the entire agreement and
understanding between Bank and Borrowers. The Loan Agreement, together with this
Fourth Amendment, and all documents executed and delivered herewith, supersede
all prior agreements and understandings relating to subject matter hereof. This
Fourth Amendment together with the Loan Agreement, and the documents executed
and delivered in connection herewith and therewith shall be construed as one
agreement, and in the event of any inconsistency, the provisions of any
promissory note evidencing a portion of the Indebtedness shall control over the
provisions of this Fourth Amendment.

                  7.2 Counterparts. This Fourth Amendment may be executed in any
number of counterparts and by different parties on separate counterparts, each
of which counterparts, when so executed and delivered, shall be deemed to be an
original and all of which counterparts, taken together, shall constitute but one
and the same agreement. This Fourth

                                       3
<PAGE>

Amendment shall be effective upon the execution and delivery of a counterpart
hereof by each of the parties hereto.

                  7.3 Captions. The captions or headings in this Fourth
Amendment are for convenience of reference only and in no way define, limit, or
describe the scope or intent of any provision of this Fourth Amendment.

                  7.4 Successors and Assigns; Governing Law. This Fourth
Amendment shall be binding upon and inure to the benefit of the respective
parties hereto and their successors and assigns and shall be governed by, and
construed and enforced in accordance with, the internal laws of the Commonwealth
of Pennsylvania without regard to its principles of conflicts of laws.

                            [signature page follows]

                                       4
<PAGE>

         IN WITNESS WHEREOF, the undersigned have executed this Fourth Amendment
as of the day and year first written above.

                                        BANK:

                                           FIRST UNION NATIONAL BANK
                                           (successor to CoreStates Bank, N.A.)

                                           By:
                                              ----------------------------------
                                                    James Conville
                                                    Assistant Vice President

                                        BORROWERS:

                                           UNITED STATES LIME & MINERALS, INC.
Attest:

By:                                        By:
   --------------------------------           ----------------------------------
   Larry T. Ohms, Controller,                 Timothy W. Byrne, President and
   Secretary, and Treasurer                       Chief Executive Officer

                                           TEXAS LIME COMPANY

By:                                        By:
   --------------------------------           ----------------------------------
   Larry T. Ohms, Controller,                 Timothy W. Byrne, President
   Secretary and Treasurer

                                           ARKANSAS LIME COMPANY

By:                                        By:
   --------------------------------           ----------------------------------
   Larry T. Ohms, Controller,                 Timothy W. Byrne, President
   Secretary and Treasurer

                                       5<PAGE>
                                                                   EXHIBIT 10(x)

                                     SECOND
                              AMENDED AND RESTATED
                                      NOTE

$5,000,000                                                        April 26, 2001

         FOR VALUE RECEIVED, UNITED STATES LIME & MINERALS, INC., a Texas
corporation (formerly known as Scottish Heritable, Inc.), TEXAS LIME COMPANY, a
Texas corporation, and ARKANSAS LIME COMPANY, an Arkansas corporation
(collectively referred to herein as "Borrowers"), jointly and severally promise
to pay to the order of FIRST UNION NATIONAL BANK (successor to CoreStates Bank,
N.A.), its successors and assigns ("Bank"), the lesser of (x) Five Million
Dollars ($5,000,000) or (y) the aggregate unpaid principal amount of all Cash
Advances made by Bank to Borrowers or any Borrower under the Amended and
Restated Loan and Security Agreement dated December 30, 1997, by and among
Borrowers and Bank (as the same has been amended and may hereafter be amended,
restated, supplemented or otherwise modified and in effect from time to time,
the "Loan Agreement"), which principal amount and all accrued and unpaid
interest thereon and Bank's Costs pertaining thereto shall be payable on the
Revolving Credit Termination Date.

         This Second Amended and Restated Note (this "Note") replaces Borrowers'
Amended and Restated Note dated December 30, 1997 in the original principal
amount of $4,000,000 (replacing Borrowers' Note dated October 20, 1993 in the
original principal amount of $6,000,000), but does not evidence repayment
thereof. This Note is issued pursuant to and entitled to the benefits of the
Loan Agreement to which reference is hereby made for a more complete statement
of the terms and conditions with respect hereto. All initially capitalized terms
used herein shall have the same meanings as ascribed to them in the Loan
Agreement unless the context clearly requires to the contrary.

         Borrowers promise to pay interest on the unpaid principal amount of all
Cash Advances from the date made to maturity (whether by acceleration or
otherwise) or earlier repayment, in accordance with Section 2.2.2 of the Loan
Agreement.

         Interest shall be payable on the outstanding principal balance hereof
as set forth in Section 2.4.5 of the Loan Agreement, at the Interest Rate Option
selected pursuant to Section 2.4.2 of the Loan Agreement. Interest shall be
calculated on the basis of a 360 day year, and charged for the number of days
actually elapsed during any year or part thereof.

         This Note may be prepaid at the times, in the amounts and with the
prepayment premiums set forth in Section 2.4.8 of the Loan Agreement.

         All payments hereunder shall be made by Borrowers jointly and severally
without defense, set off, or counterclaim and in same day funds and delivered to
Bank not later than 12:00 noon (Philadelphia time) on the date due at Bank's
office located at 1339 Chestnut Street, 11th Floor, Widener Building,
Philadelphia, PA 19107, or such other place as shall be designated in writing
for such purpose in accordance with the terms of the Loan Agreement.

                                       1
<PAGE>

         Each Borrower authorizes Bank to charge such Borrower's demand deposit
account with Bank in order to cause timely payment to be made to Bank of all
principal, interest and fees hereunder as provided in Section 1.5 of the Loan
Agreement.

         Whenever any payment on this Note shall be stated to be due on a day
which is not a Business Day, such payment shall be made on the next succeeding
Business Day and such extension of time shall be included in the computation of
interest on this Note.

         Any principal payment hereon not paid when due, and to the extent
permitted by applicable law, any interest payment hereon not paid when due, and
any other amount due to Bank hereunder, under the Loan Agreement or under any
other Loan Document not paid when due, in any case whether at stated maturity,
by notice of prepayment, by acceleration or otherwise, shall thereafter bear
interest payable upon demand at a rate which is, with respect to Adjusted LIBOR
Loans only, 5% per annum in excess of the Adjusted LIBOR until the expiration of
the then applicable Interest Period, and after the expiration of the then
applicable Interest Period, and in all cases with respect to Base Rate Loans, at
a rate which is 2.75% per annum in excess of the Base Rate.

         It shall be an event of default hereunder if an Event of Default shall
have occurred under the Loan Agreement (a "Default"). In addition to other
remedies of Bank as set forth in this Note, the Loan Agreement, or any other
Loan Document, upon the occurrence of a Default which shall be continuing, Bank
may, without demand, by written notice to Borrowers, cause this Note to become
immediately due and payable in the manner, upon the conditions and with the
effect provided in the Loan Agreement.

         THE FOLLOWING SETS FORTH A WARRANT OF ATTORNEY TO CONFESS JUDGMENT
AGAINST BORROWERS OR ANY BORROWER. IN GRANTING THIS WARRANT OF ATTORNEY TO
CONFESS JUDGMENT AGAINST BORROWERS OR ANY BORROWER, EACH BORROWER, FOLLOWING
CONSULTATION WITH (OR DECISION NOT TO CONSULT WITH) SEPARATE COUNSEL FOR SUCH
BORROWER, AND WITH KNOWLEDGE OF THE LEGAL EFFECT HEREOF, HEREBY WAIVES ANY AND
ALL RIGHTS SUCH BORROWER HAS, OR MAY HAVE TO PRIOR NOTICE AND AN OPPORTUNITY TO
BE HEARD UNDER THE CONSTITUTIONS AND LAWS OF THE UNITED STATES AND THE
COMMONWEALTH OF PENNSYLVANIA. EACH BORROWER SPECIFICALLY ACKNOWLEDGES THAT BANK
HAS RELIED ON THIS WARRANT OF ATTORNEY IN GRANTING THE FINANCIAL ACCOMMODATIONS
DESCRIBED HEREIN.

         EACH BORROWER IRREVOCABLY AUTHORIZES AND EMPOWERS ANY ATTORNEY OF ANY
COURT OF RECORD TO APPEAR FOR SUCH BORROWER IN ANY AND ALL ACTIONS, AND UPON THE
OCCURRENCE OF A DEFAULT TO: (I) ENTER JUDGMENT AGAINST SUCH BORROWER FOR THE
PRINCIPAL SUM HEREOF; OR (II) SIGN FOR SUCH BORROWER AN AGREEMENT FOR ENTERING
IN ANY COMPETENT COURT AN AMICABLE ACTION OR ACTIONS TO CONFESS JUDGMENT AGAINST
SUCH BORROWER FOR ALL OR ANY PART OF THE INDEBTEDNESS; AND IN EITHER CASE FOR
INTEREST AND COSTS TOGETHER WITH A REASONABLE COLLECTION FEE. EACH BORROWER
FURTHER IRREVOCABLY AUTHORIZES AND

                                       2
<PAGE>

EMPOWERS ANY ATTORNEY OF ANY COURT OF RECORD TO APPEAR FOR AND ENTER JUDGMENT
AGAINST SUCH BORROWER AND IN FAVOR OF BANK OR ANY HOLDER HEREOF WITH RESPECT TO
AN AMICABLE ACTION OF REPLEVIN OR ANY OTHER ACTION TO RECOVER POSSESSION OF ANY
COLLATERAL. EACH BORROWER WAIVES ALL RELIEF FROM ANY AND ALL APPRAISEMENT OR
EXEMPTION LAWS NOW IN FORCE OR HEREAFTER ENACTED. IF A COPY OF THIS NOTE,
VERIFIED BY AFFIDAVIT OF AN OFFICER OF BANK OR ANY OTHER HOLDER HEREOF, SHALL BE
FILED IN ANY PROCEEDING OR ACTION WHEREIN JUDGMENT IS TO BE CONFESSED, IT SHALL
NOT BE NECESSARY TO FILE THE ORIGINAL HEREOF AND SUCH VERIFIED COPY SHALL BE
SUFFICIENT WARRANT FOR ANY ATTORNEY OF ANY COURT OF RECORD TO APPEAR FOR AND
CONFESS JUDGMENT AGAINST EACH BORROWER AS PROVIDED HEREIN. JUDGMENT MAY BE
CONFESSED FROM TIME TO TIME UNDER THE AFORESAID POWERS WHICH SHALL NOT BE
EXHAUSTED BY ONE EXERCISE THEREOF.

         Borrowers hereby individually and collectively waive presentment,
demand for payment, notice of dishonor, protest or notice of protest and any and
all notices or demands and, to the full extent permitted by law, the right to
plead any statute of limitations as a defense to any demand hereunder in
connection with the delivery, acceptance or enforcement of this Note. The joint
and several liabilities and obligations of Borrowers hereunder shall be
unconditional without regard to the liability or obligations of any other party
and shall not be in any manner affected by any indulgence whatsoever granted or
consented to by Bank, including, but not limited to, any extension of time,
renewal, waiver or other modification. Any failure of Bank to exercise any right
hereunder shall not be construed as a waiver of the right to exercise the same
or any other right at any time and from time to time thereafter.

         This Note shall be governed as to its validity, interpretation and
effect by the internal laws of the Commonwealth of Pennsylvania. Any and all
actions at law or in equity relating to this Note and the Indebtedness shall be
brought, and jurisdiction may be had, in the courts of Philadelphia County,
Pennsylvania, or at the election of the holder hereof, the United States
District Court for the Eastern District of Pennsylvania. Borrowers consent in
advance to service of process by registered mail, return receipt requested, to
the address set forth in Section 9.3 of the Loan Agreement.

         EACH BORROWER AND BANK EXPRESSLY WAIVE ANY RIGHT TO TRIAL BY JURY IN
ANY ACTION BROUGHT BY ANY PARTY WITH RESPECT TO THE INDEBTEDNESS OR ANY LOAN
DOCUMENT.

         This Note may not be changed or amended orally but only by an agreement
in writing and signed by the party against whom enforcement of any waiver,
change, modification or discharge is sought.

         This Note is entitled to the benefits of certain other Loan Documents.

         If any provision of this Note shall for any reason be held to be
invalid or unenforceable, such invalidity or unenforceability shall not affect
any other provision hereof, but this Note shall be construed as if such invalid
or unenforceable provision had never been contained herein.

                                       3
<PAGE>

Borrowers promise to pay all Bank's Costs and expenses, including reasonable
attorneys' fees, as provided in Section 1.6 of the Loan Agreement, incurred in
the collection and enforcement of this Note. Each Borrower and endorsers of this
Note hereby consent to renewals and extensions of time at or after the maturity
hereof, without notice.

         IN WITNESS WHEREOF, and intending to be legally bound hereby, Borrowers
have executed this Note, as an instrument under seal, the day and year first
above written.

                                UNITED STATES LIME & MINERALS, INC.

                                BY:    /s/ Timothy W. Byrne
                                       -----------------------------------------
                                       TIMOTHY W. BYRNE, PRESIDENT

                                TEXAS LIME COMPANY

                                BY:    /s/ Timothy W. Byrne
                                       -----------------------------------------
                                       Timothy W. Byrne, President

                                ARKANSAS LIME COMPANY

                                By:    /s/ Timothy W. Byrne
                                       -----------------------------------------
                                       Timothy W. Byrne, President

                                       4
<PAGE>

                              TRANSACTIONS ON NOTE

<Table>
<Caption>
                                                             Outstanding
                                             Amount of        Principal
                        Amount of Loan     Principal Paid      Balance
        Date            Made This Date       This Date        This Date    Notation Made By
        ----            --------------     --------------    -----------   ----------------
<S>                     <C>               <C>                <C>           <C>

</Table>

                                       5

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00035-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00035-of-00352.parquet"}]]