##### 



Exhibit 10.28
 CONFIDENTIAL
 
 STOCK PURCHASE AGREEMENT
 
 Among
 OGLEBAY NORTON COMPANY,
 O-N MINERALS COMPANY,
 O-N MINERALS (LIME) COMPANY
 and
 UNITED STATES LIME & MINERALS, INC.
 Dated
 December ____, 2005




---



##### 



TABLE OF CONTENTS
 PageARTICLE I DEFINITIONS; CONSTRUCTION
    
    
    11.1 Definitions
    
    
    11.2 Construction
    
    
    7ARTICLE II THE SALE AND PURCHASE
    
    
    82.1 Closing
    
    
    82.2 Sale and Purchase of Sale Shares
    
    
    82.3 Purchase Price
    
    
    82.4 Closing Matters
    
    
    82.5 Purchase Price Working Capital Adjustment
    
    
    9ARTICLE III REPRESENTATIONS AND WARRANTIES OF SELLERS
    
    
    113.1 Organization and Authority
    
    
    113.2 Authorization; Enforceability
    
    
    113.3 Shares; Capitalization
    
    
    113.4 No Violation of Laws or Agreements; Consents
    
    
    123.5 Financial Statements; Books and Records
    
    
    123.6 No Changes
    
    
    133.7 Taxes
    
    
    143.8 Owned and Leased Property; Condition of Assets
    
    
    163.9 Condition of Assets
    
    
    173.10 No Pending or Threatened Litigation
    
    
    173.11 Compliance With Law; Permits
    
    
    173.12 Intellectual Property Rights
    
    
    183.13 Labor Matters
    
    
    183.14 Employees: Employee Related Agreements and Plans; ERISA
    
    
    193.15 Environmental Matters
    
    
    213.16 Bank Accounts
    
    
    223.17 Material Contracts
    
    
    223.18 Brokers, Finders, Etc
    
    
    233.19 Insurance
    
    
    233.20 Inventories
    
    
    243.21 Product Liability
    
    
    243.22 Significant Customers and Suppliers
    
    
    243.23 Accounts Receivable
    
    
    243.24 Disclosure
    
    
    24ARTICLE IV REPRESENTATIONS AND WARRANTIES OF BUYER
    
    
    254.1 Organization
    
    
    254.2 Authorization; Enforceability
    
    
    25




---



##### 



Page4.3 No Violation of Laws; Consents
    
    
    254.4 No Pending Litigation or Proceedings
    
    
    254.5 Brokers, Finders, Etc
    
    
    254.6 Investment
    
    
    254.7 Financial Ability
    
    
    26ARTICLE V [Intentionally Left Blank]
    
    
    26ARTICLE VI ADDITIONAL AGREEMENTS
    
    
    266.1 Use of Names
    
    
    266.2 Tax Matters
    
    
    266.3 Employees and Plans
    
    
    296.4 Insurance
    
    
    316.5 No Public Announcement
    
    
    316.6 Expenses
    
    
    316.7 Covenant Not to Compete
    
    
    316.8 Further Assurances and Cooperation
    
    
    326.9 Regarding Accounting, Financial Statements, and SEC Reporting
    
    
    326.10 Indemnification
    
    
    336.11 Consents
    
    
    336.12 Groundwater Monitoring Program
    
    
    336.13 Accounts Receivable
    
    
    336.14 Infringement Liability
    
    
    336.15 Trapezoid Parcel
    
    
    346.16 Master Lease and License Arrangements
    
    
    346.17 Defense of Certain Disclosed Litigation and Claims
    
    
    34ARTICLE VII CONDITIONS TO CLOSING
    
    
    357.1 Conditions Precedent to Obligation of Buyer
    
    
    357.2 Conditions Precedent to Obligation of Sellers
    
    
    35ARTICLE VIII INDEMNIFICATION
    
    
    358.1 Survival of Representations, Warranties, Covenants and Agreements
    
    
    358.2 General Indemnification
    
    
    368.3 Procedures
    
    
    378.4 Consequential Damages
    
    
    408.5 Sole Remedy
    
    
    408.6 Costs
    
    
    40ARTICLE IX MISCELLANEOUS
    
    
    409.1 Books and Records
    
    
    409.2 Notices
    
    
    419.3 Assignment; Governing Law
    
    
    429.4 Amendment and Waiver; Cumulative Effect
    
    
    439.5 No Third Party Beneficiaries
    
    
    43




---



##### 



Page9.6 Severability
    
    
    439.7 Multiple Counterparts
    
    
    449.8 Joint Drafting
    
    
    449.9 Entire Agreement
    
    
    44




---



##### 



LIST OF SCHEDULES
 Note: Schedules
Omitted. Registrant agrees to furnish supplementally a copy of any
omitted Schedules to the Commission upon request.
 Schedule 1.1A -
    
    Closing Net Working CapitalSchedule 1.1B -
    
    Permitted EncumbrancesSchedule 3.3 -
    
    Shares; CapitalizationSchedule 3.4(a) -
    
    No Violation of Laws or AgreementsSchedule 3.4(b) -
    
    ConsentsSchedule 3.5 -
    
    Financial Statements; Books and RecordsSchedule 3.6 -
    
    No ChangesSchedule 3.7 -
    
    TaxesSchedule 3.8(a) -
    
    Owned Real PropertySchedule 3.8(b) -
    
    Leases of Real PropertySchedule 3.8(d) -
    
    Shared FacilitiesSchedule 3.8(e) -
    
    Rights in the AssetsSchedule 3.9 -
    
    Condition of AssetsSchedule 3.10 -
    
    No Pending or Threatened LitigationSchedule 3.11(a) -
    
    Compliance With LawSchedule 3.11(b) -
    
    PermitsSchedule 3.12(a) -
    
    Intellectual Property AgreementsSchedule 3.12(b)(i) -
    
    Rights in Intellectual PropertySchedule 3.12(b)(ii) -
    
    PatentsSchedule 3.12(b)(iii)
-
    
    MarksSchedule 3.13-
    
    Labor MattersSchedule 3.14(a) -
    
    List of PlansSchedule 3.14(b) -
    
    Status of PlansSchedule 3.14(c) -
    
    LiabilitiesSchedule 3.14(d) -
    
    ContributionsSchedule 3.14(f)(i) -
    
    EmployeesSchedule 3.14(f)(ii) -
    
    EmployeesSchedule 3.15-
    
    Environmental MattersSchedule 3.15(c) -
    
    PermitsSchedule 3.16-
    
    Bank AccountsSchedule 3.17-
    
    Material ContractsSchedule 3.18-
    
    Brokers, Finders, Etc.Schedule 3.19(a) -
    
    Insurance PoliciesSchedule 3.19(b) -
    
    Insurance ClaimsSchedule 3.20-
    
    InventoriesSchedule 3.21-
    
    Product LiabilitySchedule 3.22-
    
    Significant Customers and SuppliersSchedule 3.23 -
    
    Accounts Receivable




---



##### 



List of Exhibits
 Note:
Exhibits Omitted. Registrant agrees to furnish supplementally a copy
of any omitted Exhibits to the Commission upon request.
 Exhibit A
    
    Opinion of Sellers CounselExhibit B
    
    Escrow Agreement




---



##### 



STOCK PURCHASE AGREEMENT
 Agreement th Parent O-N Minerals O-N Lime Sellers Buyer
 INTRODUCTORY STATEMENTS
 A.
    
    Sellers directly or indirectly own all of the issued and outstanding capital stock of O-N
Minerals (St. Clair) Company, a Delaware corporation (the Sale Shares and the Company,
respectively).
 B.
    
    On the terms and subject to the conditions set forth in this Agreement, O-N Lime desires to
sell to Buyer, and Buyer desires to purchase from O-N Lime, the Sale Shares.
  ARTICLE I
DEFINITIONS; CONSTRUCTION
 1.1 Definitions Section 1.1
 Accounts Receivable Section 3.23
 Affected Employees Section 6.3(a)
 Affiliate
 Affiliated Group Section 3.7(a)
 Agreement
 Applicable Contract
 ATF Section 3.15(c)
 Balance Sheet Section 3.5(a)




---



##### 



Balance Sheet Date Section 3.5(a)
 Business
 Business Day
 Buyer
 Buyer Benefit Programs Section 6.3(a)
 Closing Section 2.1
 Closing Balance Sheet Section
2.5(a) Section 2.5(b)
 Closing Date Section 2.1
 Closing Net Working Capital Schedule 1.1A
 COBRA Section 3.14(c)(ii)
 Code
 Company
 Company Share Transfer Section 2.2
 Competitive Business Section 6.7
 Contract Contracts
 DEQ Section 6.12
 Earnest Money Deposit
 Encumbrance




---



##### 



Environmental Law
 ERISA
 ERISA Affiliate
 Escrow Agent Section 2.4(h)
 Escrow Agreement Section 2.4(h)
 Escrow Amount Section 2.4(h)
 Expenses
 Financial Statements Section 3.5(a)
 GAAP
 Governing Documents
 Governmental Authority
 Hazardous Substance




---



##### 



Income Tax
 Indebtedness
 Indemnified Party Section 8.2(a)
 Indemnifying Party Section 8.2(a)
 Independent Auditors Section 2.5(c)
 Intellectual Property Assets Marks Section 6.1 Patents
 IP Liability Section 6.14
 Knowledge
 Law
 Leased Real Property Section 3.8(b)
 Lime Kiln Dust
 Litigation
 Losses Section 8.2(c)




---



##### 



Marks
 Master Leases and Licenses Schedule 3.4(b)
 Material Adverse Effect
 Multiemployer Plan
 Non-Competition Party
 Non-Competition Period
 Non-Competition Products
 Objection Notice Section 2.5(b)
 O-N Minerals
 Owned Real Property Section 3.8(a)
 O-N Lime
 OPDES Section 6.12
 Parent
 Party
 Patents
 Peg Amount
 Permits Section 3.11(b)
 Permitted Encumbrances




---



##### 



Schedule
1.1B
 Person
 Pre-Closing Period Section 3.7(c)
 Proceedings Section 8.2(a)
 Purchase Price Section 2.3
 Related Party
 Remedial Action Section 8.3(g)(i)
 Reserved Names Section 6.1
 Sale Shares
 Schedules
 Section 338(h)(10) Election Section 6.2(g)
 Securities Act Section 4.6
 SEC Section 6.9(a)
 Sellers
 Sellers 401(k) Plan
 Sellers Employee Benefit Plan




---



##### 



provided
 Sellers Knowledge
 Settlement Date Section 2.5(b)
 Straddle Period Section 3.7(c)
 Tax
 Tax Matters Section 6.2(c)(i)
 Tax Return
 Territory
 Title Company Section 2.4(h)
 Title Policy Section 2.4(h)
 Trapezoid Parcel Schedule
3.8(e)
 WARN Act
 Working Capital Adjustment Amount Section 2.5(d)
 1.2 Construction
 (a)




---



##### 



(b)
 (c)
 (d)
 (e)
 ARTICLE II
THE SALE AND PURCHASE
 2.1 Closing Article VII Closing llp, Closing Date
 2.2 Sale and Purchase of Sale Shares Company Share Transfer
 2.3 Purchase Price Purchase Price plus minus Section 2.4(a) (g) 2.5(d)
 2.4 Closing Matters
 (a) Section 2.3(a)
 (b)




---



##### 



(c)
 (d)
 (e)
 (f) Exhibit A
 (g) Exhibit
B Escrow Agreement Escrow Amount Escrow Agent
 (h)
 Title Company Title
Policy
  (i)
 (j)
 2.5 Purchase Price Working Capital Adjustment .
 Closing Balance Sheet Schedule
1.1A




---



##### 



Objection Notice
 Independent Auditors
 Section 2.5 Working Capital Adjustment Amount




---



##### 



ARTICLE III
REPRESENTATIONS AND WARRANTIES OF SELLERS
  3.1 Organization and Authority
 3.2 Authorization; Enforceability
 3.3 Shares; Capitalization
 (a) Sale Shares Schedule
3.3
 (b) Transfer of Title




---



##### 



3.4 No Violation of Laws or Agreements; Consents
 (a) No Violation of Laws or Agreements Schedule
3.4(a)
       (b) Consents Schedule 3.4(b)
 3.5 Financial Statements; Books and Records .
 (a) Financial Statements Schedule
3.5 Schedule 3.5 Balance Sheet , Balance Sheet Date Schedule 3.5




---



##### 



(b)
 3.6 No Changes Schedule 3.6
 (a)
 (b)
 (c)
 (d)
 (e)
 (f)
 (g)
 (h)




---



##### 



(i)
 (j)
 (k)
 (l) Schedule 3.6
 (m)
 (n)
 (o)
 3.7 Taxes
 (a) Affiliated Group Affiliated Group
 (b) Liabilities Schedule 3.7
  Schedule 3.7
 (c) Straddle Periods Schedule 3.7 Straddle Period Pre-Closing Period




---



##### 



(d) Audits; Examinations Schedule 3.7
    (e) Agreements Schedule 3.7
 (f) Consolidated Returns Schedule 3.7
 (g)
 (h) Schedule 3.7
 (i) Schedule 3.7
 (j)




---



##### 



(k)
 (l)
 (m)
 (n)
 (o)
 (p) Schedule 3.7
 (q)
 (r)
 3.8 Owned and Leased Property; Condition of Assets
 (a) Owned Real Property Schedule 3.8(a) Owned Real
Property Schedule 3.8(a)
 (b) Leases of Real Property Schedule 3.8(b) Schedule 3.8(b) Schedule 3.8(b)




---



##### 



(c) Personal Property
 (d) Shared Facilities Schedule 3.8(d)
 (e) Rights in the Assets Schedule 3.8(e)
 3.9 Condition of Assets Schedule 3.9
 3.10 No Pending or Threatened Litigation Schedule 3.10
 (a)
 (b)
 (c)
 3.11 Compliance With Law; Permits .
 (a) Compliance With Law Schedule 3.11(a) Section 3.15
 (b) Permits Schedule 3.11(b) Section 3.15 Permits




---



##### 



3.12 Intellectual Property Rights
 (a) Intellectual Property Agreements . Schedule 3.12(a)
 (b) Rights in Intellectual Property .
 In General Schedule 3.12(b)(i) Schedule 3.12(b)(i)
 Patents Schedule 3.12(b)(ii) Schedule 3.12(b)(ii) Schedule 3.12(b)(ii)
 Marks Schedule 3.12(b)(iii) Schedule 3.12(b)(iii) Schedule 3.12(b)(iii)
 3.13 Labor Matters Schedule 3.13




---



##### 



3.14 Employees; Employee Related Agreements and Plans; ERISA
 (a) List of Plans . Schedule 3.14(a)
 (b) Status of Plans . Schedule 3.14(b)
 (c) Liabilities
 Schedule 3.14(c)
 COBRA




---



##### 



Schedule 3.14(c)
   Schedule 3.14(c)
 (d) Contributions . Schedule 3.14(d)
 (e) Tax Qualification .




---



##### 



(f) Employees
 Schedule 3.14(f)(i) Schedule 3.14(f)(i)
 Schedule 3.14(f)(ii) Schedule 3.14(f)(ii)
 Schedule 3.14(f)(ii)
 (g) No Multiemployer Plans
 3.15 Environmental Matters Schedule 3.15
 (a) Compliance
 (b) Claims




---



##### 



(c) Permits Schedule 3.15(c) ATF
 (d) Notice
 (e) Listed Properties
 (f) Hazardous Substances
 (g) Required Notice or Consent
 3.16 Bank Accounts Schedule 3.16
 3.17 Material Contracts Schedule 3.17




---



##### 



take or pay meet or release most favored nations Schedule 3.17
 3.18 Brokers, Finders, Etc Schedule 3.18 Schedule 3.18
 3.19 Insurance
 (a) Policies Schedule 3.19(a) Section 6.4
 (b) Claims Schedule 3.19(b)
 (c) Post-Closing Litigation and Claims Costs . Schedule 3.10 Schedule 3.19(b)




---



##### 



Schedule
3.10 Schedule 3.19(b)
 3.20 Inventories Schedule 3.20 Schedule 3.20 Schedule 3.20
 3.21 Product Liability Schedule 3.21
 3.22 Significant Customers and Suppliers Schedule 3.22
 3.23 Accounts Receivable Accounts Receivable Schedule 3.23
 3.24 Disclosure




---



##### 



ARTICLE IV
REPRESENTATIONS AND WARRANTIES OF BUYER
  4.1 Organization
 4.2 Authorization; Enforceability
 4.3 No Violation of Laws; Consents
 4.4 No Pending Litigation or Proceedings
 4.5 Brokers, Finders, Etc
 4.6 Investment Securities Act




---



##### 



4.7 Financial Ability
 ARTICLE V
[Intentionally Left Blank]
 ARTICLE VI
ADDITIONAL AGREEMENTS
 6.1 Use of Names Section 3.12 Reserved Names
 (a)
 (b)
 (c)
 6.2 Tax Matters
 (a) Liability for Taxes
 Article VIII provided however




---



##### 



Article VIII
 Section 6.2(a)(i) Section 6.2(a)(ii) provided however
 Section 6.2(a)




---



##### 



(b) Tax Returns
  Section 6.2(b)(i) Article VIII
 (c) Tax Audits
 Tax Matters Article VIII
 Article VIII provided however
 Section 6.2(c)(ii)




---



##### 



provided however Article
VIII
 (d) Assistance and Cooperation
 Section 6.2(b)
  Section 6.2
 Section 6.2
 (e) Disputes Section 6.2
 (f) Purchase Price Adjustment Section 6.2
 (g) Section 338 Election Section 338(h)(10) Election
 6.3 Employees and Plans
 (a) Notice to Employees Section 6.3




---



##### 



Affected Employees Buyer Benefit Programs
 (b) Credit for Prior Service
 (c) Vacation
 (d) Existing Claims
 (e) COBRA
 (f) Disability
 (g) WARN Act




---



##### 



(h) Sellers 401(k) Plan Section 6.3
 6.4 Insurance
 (a) Termination by Sellers
 (b) Information
 6.5 No Public Announcement provided however
 6.6 Expenses
 6.7 Covenant Not to Compete; Covenant Not to Solicit
 (a) Competitive
       Business provided however
    (b) provided however
 6.8 Further Assurances and Cooperation
 6.9 Regarding Accounting, Financial Statements, and SEC Reporting
 (a) SEC
 (b)
 (c)




---



##### 



6.10 Indemnification
 6.11 Consents .
 6.12 Groundwater Monitoring Program . Article VIII DEQ OPDES provided however
 6.13 Accounts Receivable .
 6.14 Infringement Liability . Article
VIII IP Liability
 (a)
 (b) Section 6.14 Article VIII




---



##### 



6.15 Trapezoid Parcel . Article VIII Article VIII
 6.16 Master Lease and License Arrangements .
 6.17 Defense of Certain Disclosed Litigation and Claims . Schedule 3.10 Schedule
3.19(b)




---



##### 



ARTICLE VII
CONDITIONS TO CLOSING
 7.1 Conditions Precedent to Obligation of Buyer
 (a) Orders; Litigation .
 (b) Share Certificates and Instruments of Transfer
 (c) Other Documents
 7.2 Conditions Precedent to Obligation of Sellers
 (a) Orders; Litigation .
 ARTICLE VIII
INDEMNIFICATION
 8.1 Survival of Representations, Warranties, Covenants and Agreements Article VIII Article III Article IV




---



##### 



Section 8.1 Section 8.3 Section 3.2 Authorization Section 3.3(a) Capitalization Section 3.3(b) Title Section 3.7 Taxes Section 6.2 Taxes Section 3.14 (Employees;
Employee Related Agreements and Plans; ERISA) provided however Section 3.15 Environmental Matters Section 6.12 Article VIII Article VI
 8.2 General Indemnification Section 8.1
 (a) Indemnification by Sellers and Buyer Indemnifying Party Indemnified Party Proceedings
 Article III Article IV




---



##### 



.
 Section 8.2(a) provided however Section 6.2(a) Taxes Section 3.2 Authorization Section 3.3(a) Capitalization Section 3.3(b) Title Section 3.18 Brokers and Finders Article
VIII Article VIII
 (b) Limitations Article III Article VI
   (c) Losses provided however Section 8.5
 8.3 Procedures
 (a) Section 8.1 not




---



##### 



(b) Section
8.1 Section 8.3(b) Section 8.3(b)
 (c)
 (d) Section 8.3(b)
 (e) Article VIII Section 8.3(f)
 (f)




---



##### 



(g) Article VIII Section 6.15 Section 8.2(a)
 Section 8.3(g)(i) Remedial Action provided Article VIII provided however
 provided




---



##### 



Section 8.2(a)
 Section 8.1(a)
 8.4 Consequential Damages
 8.5 Sole Remedy Article VIII Section 8.5 Article VIII Article VIII Section 6.1 Reserved Names Section 6.7 Covenant
not to Compete; Covenant not to Solicit
 8.6 Costs
 ARTICLE IX
MISCELLANEOUS
 9.1 Books and Records provided however




---



##### 



9.2 Notices provided that provided further




---



##### 



Section 9.2 Section
9.2
 9.3 Assignment; Governing Law
 (a) Assignment provided however
 (b) Governing Law
 (c) Consent to Jurisdiction; Service of Process Section 9.2




---



##### 



Section
9.3(d)
 (d) Waivers Section 9.3(c)
 (e) Enforcement
 (f) Deemed Acceptance Article VIII Section 9.3 Article VIII
 9.4 Amendment and Waiver; Cumulative Effect .
 9.5 No Third Party Beneficiaries
 9.6 Severability .




---



##### 



9.7 Multiple Counterparts
 9.8 Joint Drafting
 9.9 Entire Agreement
 REMAINDER OF PAGE INTENTIONALLY LEFT BLANK




---



##### 



BUYER:UNITED STATES LIME & MINERALS, INC.By:Name:Title:SELLERS:OGLEBAY NORTON COMPANYBy:Name:Title:O-N MINERALS COMPANYBy:Name:Title:O-N MINERALS (LIME) COMPANYBy:Name:Title:
 Signature Page  Stock Purchase Agreement