Bridgeport Ventures Inc.: Exhibit 4.20 - filed by newsfilecorp.com





Exhibit 4.20

FIRST MODIFICATION
LETTER OF INTENT – OPTION
AGREEMENT

In Copiapó, on August 27, 2010, there appear Nelson Onofre
Roa Barahona, National identification card No. 7.501.315 -9, Mr. Eric
Leopoldo Roa Barahona, national identification card No. 9.592.648 -7, Mr.
Gabriel Emilio Roa Barahona, national identification card No. 7.150.733
-5, and Mrs. Rosa del Carmen Roa Barahona, national identification card
No. 9.367.996 -2, who appear individually and on behalf of the legal mining
company that may be formed with respect to the mining property referred to
herein, all domiciled in Parcela 7, Nantoco, municipality of Tierra Amarilla
(hereinafter all of them together Resources S.A., represented by Francisco
Schubert Seiffert, national identification card No. 6.095824 -6, and by Mr.
Marcelo Antonino Olivares Cabrera, national identification card No. 10 703
661-K, all domiciled in the city of Santiago at No. 3,895-7 Camino del Sol,
municipality of Lo Barnechea (hereinafter indistinctly the “Buyer”), have
convened in the following modification of the Letter of Intent signed between
the parties in private instrument dated June 23 of this year, authorized by the
Notary Publico of the city of Copiapó, Mr. Hernán Cañas Valdés on the 29th of
the same month indicated, hereinafter the “LI”, in the terms that are detailed
below: 

	1. 	In accordance with the LI, once the LI was signed, that is, on June
      29, 2009, the Buyer had 30 business days to study the titles and
      preference with third parties, which once completed, if in agreement with
      its conclusions, the Buyer promised to sign the final Option
      Agreement at the latest seven days after the termination of the revision
      indicated. 
	 	 
	2. 	The parties hereby modify and substitute the above agreement, in the
      sense that Buyer will have an additional period of 120 business
      days, counted from this date, that is, until January 8, 2011 including
      this alter date, to continue with the study of the titles of the property
      and preference of third parties, including, especially the authorization
      to freely enter the mining claim subject of the LI, “Trillador 1 al 14”
      (the “Property”) for the purpose of developing all reconnaissance and
      exploration work of the Property including the execution of a geophysical
      survey (GS) and all the supplementary and accessory Works to such
      exploration work for its full and total conclusion, according to the
      convenience of the Buyer, in the terms that are indicated in number
      6 following (the "Revision on site”). The parties expressly establish that
      the Revision on Site that by virtue of this act the Seller permits
      the Buyer to carry out in the Property, does not authorize the
      latter to perform drilling work, which can only be effected once the
      respective final Option agreement has been signed. 


 

Upon expiration of the above period, if the Buyer agrees
with its conclusions, it promises to sign the final Option Agreement at the
latest seven business days after the termination of the revision indicated that
is, at the latest on Monday January 17, 2011, or before if the Seller is
notified in writing . After this last period has expired, it will be
understood that the Buyer has no interest in persevering in the execution
of the final Option agreement, when numeral 4 following becomes applicable, and
it being understood that the LI has terminated ipso facto and without any effect
after which the Buyer must abandon the Property. 

1




With regard to the purchase price agreed for the Option
Agreement and its first installment, that is to say US$ 50,000 (fifty thousand
dollars of the United States of America) to be paid when the Option agreement
was signed, considering the extension of the period convened in number 2 above,
the Buyer hereby gives an advance imputable to such first installment, of
US$ 25,000 (twenty five thousand dollars of the United States of America)
equivalent in national currency to $ 12,831,750 (twelve million eight hundred
and thirty one thousand seven hundred and fifty), in accordance with the value
of the observed dollar published by the Central Bank of Chile of $ 513.27 per
US$1 that the parties expressly agree to apply. In this act, each one of the
persons of the Seller declare that they receive such payment to their
entire satisfaction through check of Banco Security No. 4672703 of the current
account owned by the Buyer, drawn in the name of Mr. Eric Roa Barahona,
authorizing its deduction from the payment of the first installment of the
Option Agreement, if this is definitively executed. In the event that the
referred to check is protested due to lack of funds or any other reason the LI
shall be understood terminated ipso facto and without any effect, and the
Buyer must abandon the Property

	3. 	The Buyer has the facultative and unilateral right not to
      persevere in the execution of the final Option agreement at any time,
      having in such case no future obligation of any type with the
      Seller, and the payment that it makes in this act will remain in
      the hands of the Seller, without the obligation to return it, in
      the capacity of only and total indemnification for the damages that, being
      linked to the LI may have caused, including this modification. 
	 	 
	4. 	In case of advanced termination of the LI and if the Buyer does
      not persevere in the execution of the final Option Agreement, it will
      deliver to the Seller all the documents and antecedents of any
      study it may have made from the Works of Revision on Site that by virtue
      of this instrument it is expressly authorized to carry out 
	 	 
	5. 	For the purpose of free access of Río Condor Resources S.A., each one
      of the persons that corresponds to the Seller party hereby grants
      special permit of access to the Property, being able to enter with the
      personnel and machinery that it may decide for the purpose of helping the
      Buyer to decide in the best way possible the Revision on Site
      during the effectiveness of the LI, in the terms of No. 1 above. Likewise,
      it especially authorizes the Buyer to exhibit the present access
      permit before any administrative or judicial authority including for
      example the Ordinary courts of Justice, Public Ministry, Chilean Police, Investigators
      Police and any other administrative or juridical organ that may be
      required in order to materialize this special access permit. 


2





		The opposition, directly or by any intermediary, of any individual who
    is part of the Seller, will be understood as a serious violation of
    this permit authorizing the Buyer to demand any legal indemnification
    for the damages approved by the Buyer. 
	 	 
	6. 	It is agreed to increase the authorization of exploitation of the
      Seller of 2,000 to 3,000 tons per month, in the terms agreed in the
      LI. 
	 	 
	7. 	In everything that is not expressly modified in this instrument, the
      LI will continue to be fully in effect and binding for both parties, this
      instrument being understood as an integral part of it for all legal and
      contractual purposes. . 


This modification of the LI is signed and authorized in two
counterparts of the same text, each party keeping one. 

	Nelson Onofre Roa Barahona 	/s/ Nelson Onofre Roa Barahona
    
	ICI. 7.501.315-9 	   
	Seller 	   
	  	   
	Eric Leopoldo Roa Barahona 	/s/ Eric Leopoldo Roa Barahona
    
	IC 9.592.648-7 	   
	Seller 	   
	  	   
	Gabriel Emilio Roa Barahona 	/s/ Gabriel Emilio Roa Barahona
    
	IC 7.150.733-5 	   
	Seller 	   
	  	   
	Rosa del Carmen Roa Barahona 	/s/ Rosa del Carmen Roa Barahona
    
	IC 9.367.996-2 	   
	Seller 	   
	  	   
	Francisco Schubert Seiffert 	/s/ Francisco Schubert Seiffert
    
	IC 6.095.824 – 6 	   
	by Río Condor Resources S.A. 	   
	Buyer 	   
	  	   
	Marcelo Antonino Olivares Cabrera 	/s/ Marcelo Antonino Olivares Cabrera
    
	IC 10.703.661-K 	   
	by Río Condor Resources S.A. 	   
	Buyer 	   


Copiapó August 27, 2010

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