Exhibit 10.13

FROM:   EARTH SCIENCES, INC., Mark H. McKinnies

TO:     CODSA 14 S.A., ENG. PEDRO PEREZ

DATE:   JANUARY 9, 1998


RE:     LETTER AGREEMENT Between CODSA 14 S.A. ("CODSA 14")
        and EARTH SCIENCES, INC. ("ESI") AND RECURSOS
        MINERALES VENESI C.A. ("VENESI"), ESI and VENESI
        collectively as "ESI/VENESI"


OBJECTIVE - SYSTEMATIC  EXPLORATION AND EVALUATION OF THE CODSA 14 CONCESSION TO
DETERMINE THE VIABILITY OF MECHANIZED MINING OPERATIONS.

1. VENESI, wholly-owned subsidiary of ESI, will conduct a systematic exploration
program on the CODSA 14 Concession  (the  "Concession")  over a 6-8 month period
and make its report and results available to CODSA 14. Such program will include
the  preparation  of a geologic map,  evaluation of ongoing  manual  exploration
mining production,  pitting, sampling,  analysis and perhaps exploratory mining.
ESI stands behind the performance of VENESI.

2. In exchange for the program to be conducted by VENESI,  and payments of stock
in ESI and cash to CODSA  14,  CODSA 14  agrees to  negotiate  exclusively  with
ESI/VENESI on the further  development  of the Concession  including  CODSA 14's
preferential rights for the veins that may underlay the Concession.

3.  ESI/VENESI  will make advance  royalty  payments (an upfront  payment of ESI
stock and monthly payments of ESI stock and cash) to CODSA 14 during the term of
the agreement.  However, ESI or VENESI may, at their sole discretion and upon 30
days  written  notice  to  CODSA  14,  terminate  the  agreement  at  any  time.
ESI/VENESI's  only obligation upon such termination would be to provide CODSA 14
the results of any work  performed  as of the date of  termination.  The upfront
payment would consist of ESI stock of $8,000 valued at $1.50 per share plus cash
of $10,000.  Monthly  payments  would  consist of $1,867 in ESI stock  valued at
$1.50 per share plus $133 cash. See point 9 below for buyback of stock.

4.  ESI/VENESI  shall  only  be  responsible  for  the  reclamation  and  proper
environmental handling of the environmental  disturbances created as a result of
its exploration  program.  ESI/VENESI assumes no responsibility for any prior or
ongoing environmental disturbances created on the Concession or adjacent areas.

5. CODSA 14 will provide all reasonable assistance to ESI/VENESI during the term
of the agreement including but not limited to:
     A.   authorization   to  obtain   information   on  file   concerning   the
          corresponding MEM's lapsed concessions,
     B.   logistical  assistance during  exploration  program and formulation of
          any mining plan,
     C.   detailed production information for ongoing exploratory mining, and
     D.   upon joint  agreement of CODSA 14 and  ESI/VENESI,  employment  of the
          Caicarenos or another group to perform  exploratory mining in areas as
          directed  by  ESI/VENESI  (in this  case  CODSA 14 would  continue  to
          receive  its 20% of  production  as now is the case  with the  ongoing
          exploratory mining).

6.  The  assistance  noted  in  point  5.  above  will  be  supplemented  with a
professional  services  agreement with Eng. Pedro Perez,  the term of which will
run concurrent  with the CODSA 14 agreement.  Payments to Mr. Perez will consist
of monthly  amounts of cash  ($1,500  per month) and stock  ($1,500 per month at
$1.50 per share). The cash amount for February 1998 being paid now.

7. Upon successful completion of the evaluation process, CODSA 14 will negotiate
exclusively  with ESI/VENESI for the further  development of the Concession.  In
such case, ESI/VENESI will negotiate a lease of the Concession, as per the terms
set forth in Exhibit A attached hereto, under which CODSA 14 will receive either
a minimum monthly  advance  royalty of $2,000 per month or a production  royalty
which will range from  5-20%.  The details of the  royalty  calculation  are set


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forth in Exhibit B  attached  hereto.  The  production  royalty  will range on a
sliding  scale based on the grade of the pay zone  mined,  so that CODSA 14 will
receive a  proportionately  greater  amount if the  property  shows  outstanding
values.  The royalty  paid to CODSA 14 will  remain at the  minimum  level until
ESI/VENESI  has  recovered  its  investment  in  the  Concession's  development.
ESI/VENESI will have a buyout amount for the CODSA 14 royalty.

8. If  ESI/VENESI  chooses to place the property into  production,  an agreeable
plan for required  reclamation of past disturbances,  if any, will be put forth.
The cost of  implementing  that plan will be deducted from the royalty  payments
made to CODSA 14 over a one year or longer period but not reducing such payments
below the minimum level.

9. ESI/VENESI  agree to buy back the ESI stock issued to CODSA 14 and Mr. Perez,
at their  option,  at the end of six months from the date of the  agreement  for
$1.50 per share.

10.  During  the term of the  agreement  ESI/VENESI  will (a) have the  right to
examine and evaluate the production from any ongoing exploratory mining, and (b)
have a 'right of first  refusal'  to  purchase  such  production  at the routine
price.

Agreed to as of the 1st day of February, 1998



/s/ Pedro A. Perez                             /s/ Mark H. McKinnies
-------------------------------                ---------------------------------
Pedro A. Perez                                 Mark H. McKinnies
President, CODSA 14 S.A.                       President, Earth Sciences, Inc.


/s/ Jean Pasquali Z.
-------------------------------
Jean Pasquali Z.
President, Recursos Minerales VENESI C.A.




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<PAGE>



                                   EXHIBIT A
                                       to
  LETTER AGREEMENT Between CODSA 14 S.A. ("CODSA 14") and EARTH SCIENCES, INC.
             ("ESI") AND RECURSOS MINERALES VENESI C.A. ("VENESI")
                          Dated as of February 1, 1998

                                  LEASE TERMS

The Lease that may be  negotiated  among  CODSA 14, ESI and VENESI at the end of
the exploration program will include the following terms and conditions:

1. Grant of Rights The Lease  shall grant  ESI/VENESI  the  exclusive  right for
exploitation of gold and diamonds on the CODSA 14 Concession  during the term of
the Lease. All of the rights,  privileges and responsibilities  granted CODSA 14
under the Concession shall apply fully to ESI/VENESI,  which shall have the duty
to defend the Concession during the term of the Lease.

2. Term The term of the Lease shall continue so long as commercial production is
continued  from the  Concession  or the Minimum  Royalty is paid,  unless sooner
terminated.

3. Minimum and Production Royalty During the term of the Lease, ESI/VENESI shall
make  either  monthly  minimum  advance  royalty  payments  of $2,000 or monthly
production  royalty  payments based on the schedule as set forth in Exhibit B of
the Letter Agreement.  The production royalty may be reduced,  but not below the
minimum  level,  to provide  for  recovery  of  ESI/VENESI's  investment  in the
development  of the  Concession  and the costs for required  reclamation of past
environmental disturbances, if any.

4. Possession and Control of Concession During the term of the Lease, ESI/VENESI
shall be granted the exclusive  possession and control of the Concession and the
right to carry on all  lawful  activities  necessary  to  exploit  the  minerals
thereon.

5. CODSA 14's Lien CODSA 14 shall at all times hold a lien  against all material
mined from the  Concession  but not yet sold, as security for any unpaid balance
of money due under the Lease.

6. Taxes During the term of the Lease,  ESI/VENESI  shall be responsible for all
taxes related to the Concession and production therefrom,  excepting those taxes
which are due as a result of CODSA  14's  receipt of its  minimum or  production
royalty.

7. Reports and Inspections  ESI/VENESI  shall maintain  appropriate  records and
make monthly reports to CODSA 14 of its activities which will include quantities
of materials  mined and grade in sufficient  detail to calculate the  production
royalty,  if any.  CODSA 14 shall have the right,  at its risk and  expense,  to
enter the  Concession at any  reasonable  time.  Within 90 days of  termination,
ESI/VENESI will deliver CODSA 14 information and material  developed or obtained
during the term of the Lease that relates to the Concession.

8. Right to Purchase During the term of the Lease, ESI/VENESI shall have a right
of first refusal for any bona fide offer made to purchase CODSA 14's interest in
the  Concession.  ESI/VENESI  shall have the right at any time to purchase CODSA
14's  interest in the  Concession  for a payment of cash to be determined at the
end of the 6-8 month  exploration  period  based on an estimate of the  mineable
reserves  on the  Concession,  a mine  life of 5 years and a net  percent  value
calculation of the royalty that would be due CODSA 14 using a 15% discount rate.

9. Other  Terms  Other  standard  terms  shall be placed in the Lease which will
include:
     a.   Notices,
     b.   Handling controversies among the parties through arbitration,
     c.   Removal of  property  on  termination,  and
     d.   cooperation among the parties in obtaining further permits, etc.



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<PAGE>


                                   EXHIBIT B
                                       to
  LETTER AGREEMENT Between CODSA 14 S.A. ("CODSA 14") and EARTH SCIENCES, INC.
             ("ESI") AND RECURSOS MINERALES VENESI C.A. ("VENESI")
                          Dated as of February 1, 1998

                          PRODUCTION ROYALTY SCHEDULE

A production  royalty shall be due to CODSA 14 for material  mined and sold from
the Concession. Nothing in this schedule shall cause the minimum royalty paid to
CODSA 14 to be less than the amount set forth in the Lease. The determination of
the  Production  Royalty,  before any  deduction  for  recovery of  ESI/VENESI's
development costs or costs for reclamation of past  environmental  disturbances,
if any,  shall be based on the following  schedule with the meaning of the terms
used as set forth below.

================================================================================
        Grade of Ore  Material  -           Prodfuction Royalty Rate -
        Equivalent  Grade in Carats  per           % of Gross
        cubic  meter of Ore Material                 Revenues

                0.375  or less                          5%
               0.0376 to 0.4375                         6%
               0.4376 to 0.5000                         7%
               0.5001 to 0.5625                         8%
               0.5626 to 0.6250                         9%
               0.6251 to 0.6875                        10%
               0.6876 to 0.7500                        11%
               0.7501 to 0.8125                        12%
               0.8126 to 0.8750                        13%
               0.8751 to 0.9375                        14%
               0.9376 to 1.0000                        15%
               1.0001 to 1.0625                        16%
               1.0626 to 1.1250                        17%
               1.1251 to 1.1875                        18%
               1.1876 to 1.2500                        19%
             greater  than 1.2500                      20%
================================================================================

Definitions -

1.  Equivalent  Grade in Carats shall be a monthly  average  determined from the
mining activities  carried on for the month, and shall be calculated by dividing
the monthly quantity of gold,  measured in grams converted to carats at the rate
of 1 gram = 0.11275 carats, plus diamonds,  measured in carat weight,  recovered
by the total cubic meters of Ore Material processed during the calendar month.

2. Ore  Material  shall  be the  in-place,  measured  quantity  of all  material
processed for recovery of gold and/or diamonds during the calendar month.

3. Production Royalty Rate is the rate the Gross Revenues actually received from
sale of the gold and  diamond  production  that  occurred  during  the  month is
multiplied to determine the royalty for a month.  CODSA 14 may choose to receive
their royalty in kind which shall be accomplished in a mutually agreeable manner
to both parties.

4. Gross Revenue shall be the amount  actually  received from sale of a calendar
month's production less any production taxes that may be assessed at the time of
production.  To the  fullest  extent  possible  ESI/VENESI  and  CODSA  14  will
cooperate  so that  each  party is  responsible  for and pays its own  taxes and
assessments related to production and revenues from the Concession.


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