**Exhibit 4.28****Portions of this exhibit have been omitted pursuant to a request for confidential treatment filedwith the Securities and exchange Commission. The omissions have been indicated by (“***”), andeach page containing confidential information is footnoted with the phrase “FOIA ConfidentialTreatment.” The omitted text has been filed separately with the Securities and exchangeCommission.****DATE — November 1, 2002****AGREEMENT BETWEEN RIVERSIDE AND VIM FOR THE EXTRACTION AND SALE OF SILICA**This Agreement dated this 1st day of November, 2002, for a term of five (5) years, byand between VICTORVILLE INDUSTRIAL MINERALS, INC., (hereafter designated as “VIM”) whosemailing address is P.O. Box 278, Oro Grande, California, 92368 and RIVERSIDE CEMENT COMPANY, P.O.Box 158, Oro Grande, California, 92368, (hereafter designated as the “Riverside”).WHEREAS, Riverside owns and/or controls a considerable amount of real property near Oro Grande,California, upon which Riverside conducts Portland Cement manufacturing operations and relatedactivities (the “Riverside Oro Grande Property”)WHEREAS, certain portions of the Riverside Oro Grande Property contains certain deposits ofaggregates that Riverside does not intend to use in its manufacture of Portland Cement;WHEREAS, VIM desires to extract and purchase from Riverside such aggregates, and in particular,silica material, from certain designated portions of said Riverside Oro Grande Property; andWHEREAS Riverside desires to permit the extraction and subsequent sale of such aggregates andsilica materials to VIM from said certain portions of the Riverside Oro Grande Property;WITNESSETH, that the parties hereto, in consideration of the mutual promises and undertakingsherein contained, mutually agree as follows:1.) SCOPE OF SALE AND PURCHASE OF SILICA*:*VIM agrees to extract and purchase silica from sections of the Riverside Oro GrandeProperty identified on Exhibit “A” which is attached hereto and incorporated hereinby reference (the “Silica Land”). The parties acknowledge that although theRiverside Oro Grande Property encompasses more real property than is designated onExhibit “A” as the Silica Land, (i) Riverside shall have no obligation to provideareas for extraction other than the those agreed to as the Silica Land at the execution ofthis Agreement and designated on Exhibit “A”; and (ii)
1

 
  VIM shall have no right or obligation to conduct a silica operation and/or the associatedreclamation on any portion of the Riverside Oro Grande Property other than the Silica Landdesignated and/or defined for such activity on Exhibit “A” (and the designatedaccess to the Silica Land in accordance with Section 16 hereof), or pursuant to theagreement in place between Riverside and VIM dated October 1, 2001. 2.) RECLAMATION PLAN AND PERMITTING CONSISTENCY   The parties acknowledge that they will work cooperatively to bring consistency to thereclamation plans and permits, if applicable, for the work that VIM performs pursuant tothis agreement and its agreement dated October 1, 2001. To further this commitment, VIM andTXI shall continue to meet with, and work with, the County of San Bernardino to realign theboundaries for the reclamation plans depicted on the Exhibit “A” map as follows:   First, VIM shall have the boundaries for the VIM Reclamation Plan for the October 1, 2001Agreement, hereinafter referred to as TXI-I, realigned to have the green (TXI#1-A) andyellow (TXT#1-B) shaded areas marked within TXI-I expanded to include the blue shaded areacorrespondently marked TXI#1-C. The yellow area marked TXI#1-B is currently in both the VIMand TXI Reclamation Plans and the blue TXI#1-C shaded area is not currently a part of anyreclamation plan. VIM agrees to modify the TXI-I plan with the County of San Bernardino toinclude the blue shaded area TXI#1-C.   Second, VIM shall have the boundaries for its newly anticipated reclamation plan for TXI-IIconform to include the area shaded blue on the Exhibit “A” and shown as TXI#2-A. Thegreen and yellow areas marked TXI#2-B and TM#2-C respectively shall remain within thepurview of Riverside’s current reclamation plan (84M-009). VIM will initiate TMI#2 mining inthe TXI#2 B and C areas and depending on the sequencing of VIM’s Atlas Project, VIM may ormay not pursue the permitting and mining of TXI#2-A.   All haul roads, (and ingress and egress roads), of every type shall be preserved pursuant tothe agreements the parties have reached in the past, and which are memorialized by theirprior written agreements. 3.) CONDUCT OF OPERATIONS ON RIVERSIDE ORO GRANDE PROPERTY. Notwithstanding anything herein to the contrary, VIM and Riverside each acknowledge that,at all times during which VIM is conducting its silica operations and/or associatedreclamation on the Silica Land pursuant to this Agreement, (i) Riverside shall be actively conducting its portland cement manufacturingoperations and related activities on portions of the Riverside Oro Grande Propertyadjacent to and contiguous with the Silica Land; and  (ii) The designated daily access to the Silica Land shall be through a portion ofRiverside’s manufacturing operations and across roads heavily used by Riverside in itsmanufacturing operations on the Riverside Oro Grande Property; and
2

 
 (iii) Riverside has made no representation or warranty as to any conditions on orpertaining to any portion of the Riverside Oro Grande Property, the Silica Land and/oraccess to the Silica Land, and VIM accepts same “AS IS AND WITH ALL FAULTS”.  This provision shall survive the termination/expiration of this Agreement for all purposes,including but not limited to determinations of indemnification pursuant to Section 15(a)hereof. 4.) WARRANTY*:*VIM hereby affirmatively acknowledges that all silica extracted and removed from theSilica Land by VIM is extracted and removed in an “AS IS AND WITH ALL FAULTS”condition for all purchases (the extraction and removal) of silica by VIM, pursuant to thisAgreement, and that all sales are final, and without (i) any expressed or impliedwarranties, of any type or nature, as provided for by the Uniform Commercial Code; and/or(ii) any expressed or implied warranties as to characteristics, specifications or quality(environmental or otherwise) of the silica*.* 5.) QUANTITIES*: **** 6.) TERM*:*This Agreement, commencing on the date of execution of the Agreement, shall extend throughNovember 1, 2007. Riverside shall not unreasonably withhold its consent to extend the termof this Agreement to enable VIM to complete contractual obligations it has entered intoduring the term of this Agreement, and may extend beyond the expiration date.Notwithstanding the foregoing, this Agreement may be terminated, with or without cause, byeither party upon six (6) months advanced written notice, from one party to the other. 7.) PRICING*:*VIM shall pay Riverside for all silica extracted and removed from the Silica Land in TXI Iareas at a rate of $*** per ton. VIM shall pay Riverside for all silica extracted andremoved from the TXI II areas which fall within the Riverside Reclamation Plan (TXI#2-B andTXI#2-C) at a rate of $*** per ton and $*** per ton for silica removed from TXI#2 areaswhich will fall under the VIM Reclamation Plan (area TX#2-A only) Refer to Exhibit“A” for a location of the silica lands under this agreement. Riverside shall invoice VIMon the basis of tonnage calculations provided in Section 8 below. Full payment shall be madeto Riverside at Riverside’s Oro Grande office within thirty (30) days of VIM’S receipt ofeach monthly invoice.8.) TONNAGE CALCULATIONS*:*Payment for tonnage of silica removed from the Silica Land will be determined through theuse of the applicable rate, provided above, times the number of loads removed from theSilica Land by VIM, and verified, as necessary, by Riverside as follows. Standard weightmeasurements shall be derived in the following manner: An outside neutral contractor to VIMand Riverside shall be hired to haul three   FOIA Confidential Treatment
3

 
  loads; the loads to be loaded by VIM. These loads will then be driven across VIM’s certifiedscale, as well as Riverside’s/TXI’s certified scale. The net average of the three loadsshall determine the billing rate. This procedure will be repeated every six months. Theweight for each load established by this process shall be the weight per load for allbillings between the parties for the following six-month period of time.   VIM shall deliver to Riverside each month a written statement, setting forth by weight thequantity of silica removed from the Silica Land. VIM shall keep complete records of allsilica removed from the Silica Land herein. VIM further agrees that such records shall besubject to Riverside’s inspection, upon twenty four (24) hours notice to VIM that Riversiderequests such an inspection, and upon a notice from Riverside to VIM indicating that such aninspection shall occur only during VIM’s reasonable and customary business hours ofoperation. Riverside acknowledges and agrees that only those VIM business records concerningthis Agreement for the extraction of silica are open for Riverside’s inspection. Riversidefurther acknowledges and agrees that any such inspection shall not constitute a waiver byVIM of any applicable privileges that may attach to such records, shall not constitute awaiver of the confidentiality afforded to such records, if any, and shall not constitute thewaiver of the proprietary nature of such records, if any. 9.) INDEPENDENT CONTRACTOR*:*VIM is and shall remain an independent contractor in the performance of the work,maintaining complete control of VIM’s workmen and operations. Neither VIM nor anyoneemployed or engaged by VIM shall become an agent, representative, servant, or employee ofRiverside in the performance of the work or any part thereof. 10.) PERMITS/COMPLIANCE WITH LAWS: VIM shall be fully responsible for obtaining all necessary environmental permits for itsoperations on the lands identified in this agreement. VIM is also fully responsible for thecompliance of its operations with all applicable permits, rules, regulations, and/or laws.   VIM, through execution of this agreement, agrees all work performed on the Riverside OroGrande Property will comply with the requirements applicable to the approved RiversideReclamation Plan (84M-009) dated February 23, 1984 on the Riverside Oro Grande Propertyattached hereto, and incorporated herein by this reference, as Exhibit “B”(hereinafter the “Exhibit “B” and/or “VIM’S Obligation under the TXI ReclamationPlan”) for purposes of the work to be performed in areas which fall within the RiversideReclamation Plan. VIM will comply with applicable requirements of the VIM Reclamation Plan(97M-O1) in areas which fall within this reclamation plan as defined in Exhibit “A”.Riverside will make available all necessary documentation to inform VIM of said conditionsof the Riverside Reclamation Plan (84M-009).
4

 
11.) CLEANUP*:*Unless otherwise agreed in writing by the parties at the time of termination/expiration ofthis Agreement, within six (6) months after the expiration/termination of this Agreement,VIM shall remove all equipment and unused non-native materials provided for its work, andagrees to place the Silica Land as described and/or depicted within Exhibit “A”.Furthermore, Riverside shall provide a location on its property for the placement of miningwaste materials according to the Exhibit “A”. 12.) DRUG-FREE WORK PLACE*:*VIM represents it maintains a drug free workplace policy. As a result of this existingpolicy, VIM agrees to advise its employees and the employees of its subcontractors andagents (hereinafter for the purposes of this provision collectively referred to as “VIMemployees”), that: (i) it is the policy of Riverside that the use, possession, sale,transfer, or purchase of illegal drugs on the Riverside Oro Grande Property, is prohibited;(ii) entry onto the Riverside Oro Grande Property constitutes the presence of an employee’svehicle on the Riverside Oro Grande Property and/or any personal effects of an employeewhich the employee brings with him or her while entering, on or leaving the Riverside OroGrande Property; and (iii) any employee who is found in violation of the policy or whorefuses to permit an inspection by an authorized representative of Riverside may be removedand barred from the Riverside Oro Grande Property, at the discretion of Riverside. 13.) SAFETY*:*While on the Riverside Oro Grande Property, VIM shall observe, and shall cause itssubcontractors and agents to observe, such safety rules as Riverside shall prescribe asnecessary for the protection of Riverside’s personnel and property. Riverside’s Safety Bookis attached hereto and is incorporated herein as Exhibit “C.” VIM acknowledges itsreceipt of this Safety Book. VIM further affirms its own commitment to comply with its ownsafety procedures and policies, as applicable to the work it shall be performing pursuant tothis Agreement. In addition, both parties affirm their commitment to comply with allapplicable MSHA and CAL/OSHA regulations applicable to each during the term of thisAgreement*.* 14.) INSURANCE*:*VIM acknowledges that it has and shall maintain, at its own expense, for the duration ofthis Agreement (and shall require all of its subcontractors to obtain, carry and maintainfor the duration of this Agreement), the following insurance coverage with following minimumlimits: (a) Workers Compensation as required by laws and regulations applicable toand covering employees of VIM (or the subcontractor) engaged in the performance of thework under this Agreement with the applicable statutory limits, as well as employer’sliability insurance with minimum limits of $1,000,000.  (b) A General Liability Insurance Policy covering its operations for legal liability itcauses with minimum limits of $5,000,000.
5

 
 (c) Automobile Liability of all owned and non-owned/hired vehicles withminimum limits of $1,000,000.  All insurance coverage shall be obtained from one or more insurance companies which have anA.M. Best rating of A- or better (or an equivalent rating on an equivalent rating system).   All insurance policies shall contain a waiver of subrogation; and each certificate shallname Riverside as an additional insured.   VIM agrees to notify Riverside in writing, at least thirty (30) days in advance of anysignificant modification, expiration or cancellation of any such insurance policies coveringVIM’S actions and obligations under this Agreement, including but not limited tomodifications, expiration or cancellation of insurance coverage meeting the minimumrequirements set forth in this Section 14.   VIM acknowledges that on or before the execution of this Agreement, VIM presented Riversidewith a copy of a Certificate of Currency dated April 17, 2001 evidencing VIM’S then-currentinsurance coverage. Upon execution of this Agreement, VIM shall furnish to Riverside theequivalent of a certificate of insurance describing that the above insurances are in fullforce and effect.   Notwithstanding anything herein to the contrary, VIM acknowledges that any insurancecoverage held by VIM shall not relieve or limit VIM’s obligations and/or liability pursuantto this Agreement, including but not limited to the indemnification set forth in Section 15hereof. 15.) INDEMNIFICATION AND DISPUTE RESOLUTION: (a) Indemnification: ***.  (b) Dispute Resolution: Any dispute between the Parties arising out of orrelating to this Agreement (including, without limitation, its creation,interpretation, enforcement or breach) or any document or instrument referred to herein(a “Dispute”) shall be resolved as follows:    Settlement Negotiations: The Parties in good faith shall attempt to settleany Disputes within thirty (30) days of receipt by one party from the other of anotice to this effect. If such negotiations fail to resolve the Dispute, the Partiesshall proceed as set forth below.    Arbitration: Any Dispute which is not resolved through the settlementnegotiations provided for above shall be resolved by binding arbitration before aqualified, experienced, unbiased, and neutral arbitrator selected by the Parties.   FOIA Confidential Treatment
6

 
   The arbitration shall be conducted in the State of California and governed bythe rules set forth in California’s Code of Civil Procedure sections 1281 *et seq.*,(or similarly enacted statutory guidelines for the handling of privatecontractually-based arbitration proceedings). The Arbitrator shall abide byCalifornia law in rendering his decision and shall determine which Party is entitledto recover under this Agreement, and shall provide for any other appropriate legalor equitable relief.    Jurisdiction, Venue and Choice of Law: Solely for purposes of thisAgreement, the Parties consent to jurisdiction in San Bernardino County, California.Any disputes between the parties hereunder shall be resolved, by and under the lawsof the State of California without regard to its choice of law provisions.16.) ACCESS: Riverside shall provide VIM access to the current extraction site through theRiverside Oro Grande Property by means of a designated route or area. VIM agrees thatRiverside may reasonably limited its access to the area denoted on Exhibit “A” andExhibit “B” when necessary to ’s ongoing operations, and/or any modifications to itsfacilities or planned construction currently anticipated to take place during the term of thisagreement, , but may not do so for more than any two day period of time. VIM further agrees itshall provide Riverside with timely written notice of any changes VIM requests for a differentor modified access route, and that it shall not proceed to use a different or modified accessroute without Riverside’s prior acknowledgement and consent to the same, which consent byRiverside shall not be unreasonably withheld. VIM shall provide Riverside with two days noticeof any such proposed change.17.) FUGITIVE DUST CONTROL: VIM understands Riverside is required to mitigate fugitive dustassociated with any operations on the Riverside Oro Grande property. VIM agrees to controlfugitive dust emissions associated with its extraction, processing, management andtransportation of silica materials while on the Riverside Oro Grande property, and , inparticular, within the Silica Land.18.) NOTICE: All notices given under this Agreement shall (unless otherwise expressly providedherein) be in writing and signed by the party giving such notice. it shall be deemed givenwhen personally delivered, or five (5) business days thereafter when deposited in the U.S.Mail, with proper postage prepaid and addressed to the other party at its respective followingaddress, or at such other address as either party may hereafter furnish by a notice givenpursuant thereto:   If to Riverside: Riverside Cement CompanyP.O. Box 51479Ontario, CA. 91761-0079   Attn: Kelly Salmon, Plant Manager, Oro Grande   If to VIM: Victorville Industrial Minerals, Inc.P.O. Box 278Oro Grande, CA. 92368   Attn: Jacqueline Campo, Mine Supervisor
7

 
19.) NO ASSIGNMENT*:*This Agreement, nor any obligation or right thereunder, may not be assigned by VIM withoutRiverside’s express written consent, which consent by Riverside shall not be unreasonablywithheld*.* 20.) NO PARTNERSHIP, JOINT VENTURE OR PRINCIPAL-AGENT RELATIONSHIP: Nothing contained in thisAgreement, nor any acts of the parties, shall be deemed by the parties to create therelationship of principal and agent, or of employer and employee, or of partnership, or ofjoint venture, or of any other association between the parties, and no provisions in thisAgreement are intended to create or constitute any person a third party beneficiary hereof. 21.) ENTIRE AGREEMENT: This Agreement constitutes the entire agreement between the parties on thesubject matter contained herein and supersedes any prior written or oral agreements orstatements. 22.) MODIFICATIONS AND WAIVERS*:*All modifications to this Agreement must be in writing and signed by the parties hereto.No provision of this Agreement can be waived, except in writing, signed by the party waivingsuch provision, nor shall failure to object to any breach of a provision of this Agreementwaive the right to object to a subsequent breach of the same or any other provision. 23.) SEVERABILITY: If any provision of this Agreement shall, for any reason, be held violative ofany applicable law, and so much of said Agreement is held to be unenforceable, then theinvalidity of such a specific provision herein shall not be held to invalidate any otherprovisions herein, and all other provisions herein shall remain in full force and effect.Furthermore, in lieu of such illegal, invalid, or unenforceable provision, there shall beadded automatically as a part of this Agreement a provision as similar in terms to suchillegal, invalid or unenforceable provision as may be possible and be legal, valid andenforceable. 24.) GOVERNING LAW AND COMPLIANCE WITH THE LAW: This Agreement shall be interpreted under andenforced in accordance with, and subject to, the laws of the State of California. Further,the parties agree that they shall comply with all federal, state and municipal statutes,ordinances and regulations that may apply to their respective operations, duties andresponsibilities under the terms of this Agreement, and for the duration of this Agreement. 25.) NO CONSTRUCTION AGAINST THE AUTHOR: Each party warrants and represents that it hasparticipated fully in the negotiation, preparation and drafting of this Agreement, and that thelanguage used in this Agreement is a product of that participation. The rule that an ambiguity inlanguage is to be construed against the author accordingly shall have no effect as to thisAgreement.
8

 
26.) HEADINGS: The captions to the several paragraphs hereof are not a part of this Agreement andshall have no legal significance, but are merely guides or labels to assist in locating andreading the paragraphs contained herein. 27.) FURTHER ASSURANCES: Each party agrees to do any thing and sign any documents, which arenecessary and desirable to accomplish any of the goals, terms or conditions of this Agreement. 28.) COUNTERPARTS: This Agreement may be executed in two or more counterparts, each of which shallbe deemed an original, but of which together shall constitute one and the same instrument**IN WITNESS WHEREOF**, Riverside and VIM have executed this Agreement on the day and year firstwritten above.      RIVERSIDE CEMENT COMPANY