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Exhibit 4.28 

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                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           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|   | **SEGUNDO CONVENIO    MODIFICATORIO AL CONTRATO DE PRESTACIÓN DE SERVICIOS PROFESIONALES,    CELEBRADO POR LA EMPRESA "MINERA SAN XAVIER" S.A. DE C.V., REPRESENTADA POR    EL LIC. LUIS RODOLFO RODRÍGUEZ, EN ADELANTE "MSX" Y POR LA EMPRESA "FIREX"    S.A. DE C.V., REPRESENTADA POR EL ING. JORGE MENDIZÁBAL ACEBO, EN ADELANTE "FIREX",    AL TENOR DE LOS SIGUIENTES ANTECEDENTES, DECLARACIONES Y CLÁUSULAS.**SECOND AMENDMENT    AGREEMENT TO THE PROFESSIONAL SERVICES CONTRACT, ENTERED INTO BY AND BETWEEN    THE COMPANY "MINERA SAN XAVIER, S.A. DE C.V.", REPRESENTED BY MR. LUIS    RODOLFO RODRIGUEZ (HEREINAFTER REFERRED TO AS "MSX") AND BY THE COMPANY "FIREX,    S.A. DE C.V.", REPRESENTED BY MR. JORGE MENDIZABAL ACEBO (HEREINAFTER    REFERRED TO AS "FIREX"), ACCORDING TO THE FOLLOWING ANTECEDENTS,    REPRESENTATIONS AND CLAUSES.      **A N T E C E D E N T E S .****A N T E C E D E N T S**          
PRIMERO.- Con fecha 25 de Octubre de 2004, MSX y FIREX    celebraron contrato de prestación de servicios profesionales, en virtud del    cual el segundo se comprometió con el primero a asistirle durante el    desarrollo del proyecto minero de Cerro de San Pedro, localizado en el    Municipio del mismo nombre, para lo cual se designó al Ing. Jorge Mendizábal    Acebo como asesor en funciones de Director General de dicho proyecto. La    vigencia originalmente pactada de dicho contrato fue de seis (6) meses.
FIRST.- On October 25th, 2004, MSX and FIREX entered into a    professional services contract, by which the latter committed to assist the    first, during the development of the mining project of Cerro de San Pedro,    located in the Municipality of the same name, for which Mr. Jorge Mendizabal    Acebo was appointed as advisor, acting as General Director of such project.    The term of effectiveness originally agreed for such contract was of six (6)    months.  
 
   
SEGUNDO: Con fecha 15 de Abril de 2005, las partes celebraron    un convenio modificatorio, a efecto de modificar la vigencia y el monto del    contrato  original. 
SECOND.- On Aril 15, 2005, the parties entered an amendment    agreement to the professional services contract, in order to modify the term    of effectiveness and the professional fees of such contract. 
 
 
TERCERO.- Por así convenir a los intereses de las partes,    éstas han
THIRD: Since it represents a benefit for the parties, those    have agreed to modify again
 convenido, modificar el monto de dicho    contrato, razón que justifica la celebración de este segundo convenio.the professional fees of such contract,    reason that justifies the formalization of the present second amendment    agreement.   **D E C L A R A C I O N E S .****R E    P R E S E N T A T I O N S** 
I.
Declara MSX:    

ÚNICO.- Ratificar    todas y cada una de las  declaraciones establecidas en el contrato y    convenio que se describen en los antecedentes PRIMERO y SEGUNDO de este    instrumento. 
I. Of MSX: 

UNIQUE.- To ratify    each and all the representations established on the contract and amendment    agreement described in the FIRST and SECOND antecedents of this document. 
 
 
  
II.
Declara FIREX:
II. Of FIREX:
 
 
  
 
ÚNICO.- Ratificar    todas y cada una de las declaraciones establecidas en el contrato y convenio    que se describen en los antecedentes PRIMERO y SEGUNDO de este instrumento.
UNIQUE.- To ratify    each and all the representations established on the contract and amendment    agreement described in the FIRST  and SECOND antecedents of this    document. 
 
 
  
III.
Declaran las    partes:
III. Of the    parties: 
 
a) Ratificar los    contenidos de sus respectivas declaraciones manifestadas en este instrumento    y reconocerse la personalidad y capacidad jurídica con que comparecen a    celebrar el mismo.
a) To ratify the    content  of their respective representations manifested in this    document and to acknowledge the personality and legal capacity to which they    formalize the same.  
 
b) Aceptar regular    la relación jurídica que les vincula, conforme a los términos, condiciones y    alcances de este convenio modificatorio, de conformidad y en apego al    contenido de los mismos,
b) To accept    regulate the legal relationship that binds them,  according to the    terms, conditions and scope of this amendment agreement, in accordance to    the content of the same, granting their free will, not existing deceitful 
 
otorgando su libre    acuerdo de voluntad, sin que exista para ello error, dolo, mala fe, ni    ningún otro vicio que altere su libre consentimiento, por lo que otorgan la    siguiente:
representations,    error, bad faith, nor any other act or omission that would induce the    parties to enter this agreement that they would not otherwise have made; the    parties, therefore, agree the following: **C L Á U S U L A .****C L A U S E**
    ÚNICA.- Las partes ratifican el contenido y alcances de todas y cada una de    las cláusulas contenidas en el contrato de prestación de servicios    profesionales a que se refiere el antecedente PRIMERO de este convenio, con    excepción de la cláusula TERCERA, la que se modifica y queda como sigue:    
    UNIQUE.- The parties ratify the content and scope of each and all the    clauses container in the professional services contract, referred to in the    FIRST antecedent of this document, with exception to clause THIRD, which is    hereby amended as follows: ***TERCERA.-    HONORARIOS. MSX pagará a FIREX por la prestación de servicios profesionales    descritos en la cláusula primera, la cantidad anual de US $86,250.00 (ochenta    y seis mil doscientos cincuenta dólares americanos 00/100) más el Impuesto    al Valor Agregado correspondiente, cantidad que se cubrirá en su equivalente    en moneda nacional al valor dólar fix determinado por BANXICO en el día en    que se deba realizar el pago." ***THIRD.- PROFESSIONAL FEES. MSX shall pay FIREX, for the professional    services described in clause first, a yearly fee equal to US$86,250.00    (eighty six thousand two hundred and fifty dollars 00/100 USCy) plus the    corresponding Added Value Tax, amount that shall be paid in Mexican currency    at the rate determined by BANXICO on the day on which the amount is due and    payable." 
    Leído que fue el presente convenio, las partes lo firman por duplicado, en    la ciudad de San Luis Potosí, el primer día mes de Abril de 2008. 
    Having read the parties the present agreement, they sign it in two (2)    copies, in the city of San Luis Potosi, on the 1st day of April,    2008. 
**Por/By MSX****Por/By FIREX**    **/s/ Luis Rodolfo Rodriguez****/s/ Jorge Mendizabal Acebo****LIC. LUIS RODOLFO RODRÍGUEZ****ING. JORGE MENDIZÁBAL ACEBO**  **TESTIGOS DE    ASISTENCIA****WITNESSES**      **/s/ Richard J. Hall****/s/ Carlos Gonzalez Andrade****SR. RICHARD J. HALL****LIC. CARLOS GONZÁLEZ    ANDRADE************ |