Exhibit 4.5


     THESE SECURITIES HAVE NOT BEEN REGISTERED WITH THE UNITED STATES SECURITIES
AND  EXCHANGE  COMMISSION  OR  THE  SECURITIES  COMMISSION  OF  ANY  STATE.  THE
SECURITIES  MAY NOT BE  RESOLD OR  TRANSFERRED  EXCEPT  AS  PERMITTED  UNDER THE
SECURITIES ACT OF 1933, AS AMENDED (THE "ACT"),  PURSUANT TO  REGISTRATION OR AN
EXEMPTION THEREFROM.


No. R-697                                                          US$ 1,000,000


                              EARTH SCIENCES, INC.

                  10% CONVERTIBLE DEBENTURE DUE MARCH 31, 2000

     THIS  DEBENTURE is one of a duly  authorized  issue of  Debentures of Earth
Sciences,  Inc., a corporation duly organized and existing under the laws of the
State of Colorado (the "Company"),  designated as its 10% Convertible  Debenture
Due March 31, 2000, in an aggregate principal amount not exceeding  US$1,000,000
(herein, the "Debentures").

     FOR VALUE RECEIVED,  the Company  promises to pay to Tectonic  Construction
Co., the  registered  holder  hereof (the  "Holder"),  the  principal sum of US$
1,000,000.00,  on March 31, 2000 (the "Maturity Date") together with interest on
the principal sum outstanding from time to time at the rate equal to the greater
of (I) the prime rate as reported by Bank One, Denver, Colorado plus two percent
(2%) ("Prime +2%), or (ii) ten percent (10%), per annum,  adjusted quarterly and
computed on the basis of the actual  number of days  elapsed in a 365-day  year.
All accrued  interest shall be payable in arrears,  and shall be due and payable
at the end of each calendar  quarter or, if earlier,  on the Conversion Date (as
hereinafter defined).  Accrual of interest shall commence on the date hereof and
shall  continue until payment in full of the principal sum has been made or duly
provided for. All accrued and unpaid interest so payable,  together with any and
all other  amounts  payable  hereunder,  less any amounts  required by law to be
deducted or withheld,  will be paid on the Maturity Date or, if earlier,  on the
Conversion  Date,  and shall be paid to the person in whose name this  Debenture
(or one or more  predecessor  Debentures)  is  registered  on the records of the
Company  regarding  registration and transfers of the Debentures (the "Debenture
Register") on the  Conversion  Date or tenth day prior to the Maturity  Date, as
the  case  may  be;  provided,  however,  that  the  Company's  obligation  to a
transferee  of  this  Debenture  arises  only if such  transfer,  sale or  other
disposition  is  made  in  accordance  with  the  terms  and  conditions  of the
Subscription  Agreement and Investment Agreement executed by the original Holder
in  connection   with  the  purchase  of  this  Debenture   (the   "Subscription
Agreement").  The principal  of, and interest on, this  Debenture are payable in
such coin or currency of the United  States of America as at the time of payment
is legal  tender for payment of public and private  debts,  at the address  last
appearing on the  Debenture  Register of the Company as designated in writing by
the Holder  from time to time.  The  Company  may prepay a portion or all of the
Debentures  at any time.  The Company shall provide the Holder with no less than
30 days written notice of any prepayment.  The forwarding of the Company's check
shall,  subject to  collection,  constitute a payment of interest and  principal
hereunder  and shall  satisfy and  discharge  the  liability  for  principal and
interest on this  Debenture to the extent of the sum  represented by such check.
Any payments  received by Holder will be applied in the following order: (I) any
collection  costs the  Holder  may have  incurred  in  procuring  the  Company's
performance hereunder,  (ii) payment of the interest then accrued and due on the
unpaid  principal  balance of this Debenture,  (iii) any charges assessed by the
Holder, and (iv) principal.

     This Debenture is subject to the following additional provisions:

          1. The Debentures are issuable in  denominations  of Two Hundred Fifty
Thousand Dollars (US $250,000) and integral  multiples  thereof.  The Debentures
are  exchangeable  for an equal  aggregate  principal  amount of  Debentures  of
different authorized denominations, as requested by the Holders surrendering the
same.  No service  charge  will be made for such  registration  or  transfer  or
exchange.

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<PAGE>



          2. The Company  shall be entitled  to  withhold  from all  payments of
principal  of, and  interest  on,  this  Debenture  any  amounts  required to be
withheld under the applicable provisions of the United States income tax laws or
other applicable laws at the time of such payments.

          3.   This   Debenture   has  been   issued   subject   to   investment
representations  of the  original  purchaser  hereof and may be  transferred  or
exchanged  only in compliance  with the  Securities Act of 1933, as amended (the
"Act") and the terms of the Subscription Agreement. Prior to due presentment for
transfer of this  Debenture,  the Company and any agent of the Company may treat
the person in whose name this  Debenture  is duly  registered  on the  Debenture
Register  as the owner  hereof for the  purpose of  receiving  payment as herein
provided and for all other  purposes,  whether or not this Debenture be overdue,
and  neither  the  Company nor any such agent shall be affected by notice to the
contrary.

          4. The Holder of this Debenture shall be entitled,  at any time during
the  period  commencing  on and after  November  30,  1997 and  expiring  on the
Maturity Date, to convert up to the entire  principal  amount of all outstanding
Debentures  into shares of common  stock,  par value $.01 per share (the "Common
Stock"),  of the Company at a  conversion  price for each share of Common  Stock
equal to the Market Price of the Company's  Common  Stock.  For purposes of this
Section 4, the Market  Price  shall be the  average of the closing bid prices of
the Common  Stock over the five  consecutive  trading days ending on the Closing
Date (as defined in the  Subscription  Agreement),  as reported by the  National
Association of Securities Automated Quotation System ("NASDAQ"). Such conversion
shall be effectuated by  surrendering  all of the Debentures to the Company with
the form of  conversion  notice  attached  hereto as Exhibit A,  executed by the
Holder(s) of the Debentures  evidencing  such Holder's  intention to convert the
Debentures.  The amount of accrued but unpaid interest as of the Conversion Date
shall  not be  subject  to  conversion  but  shall  be  paid  in  cash as of the
Conversion Date. No fraction of shares of the Common Stock or scrip representing
fractions  of shares will be issued on  conversion,  but the number of shares of
the Common Stock issuable shall be rounded to the nearest whole share.  The date
on which notice of  conversion  is given shall be deemed to be the date on which
the Holder  has  delivered  this  Debenture,  with the  conversion  notice  duly
executed,  to the Company,  or if earlier,  the date set forth in such notice of
conversion  if the  Debenture is received by the Company  within three  business
days  thereafter.  Such date is  referred  to herein as the  "Conversion  Date."
Facsimile  delivery of the  conversion  notice shall be accepted by the Company.
Certificates  representing Common Stock upon conversion will be delivered to the
Holder  within five (5) business  days from the date the notice of conversion is
delivered to the Company.  The conversion rights granted by this Section 4 shall
become null and void if the control of Holder no longer resides in the Robert H.
Lowdermilk family.

          5. Any of the following shall constitute an "Event of Default":

               a. The  Company  shall  default in the  payment of  principal  or
          interest  on this  Debenture  as and when  the  same  shall be due and
          payable and such default  shall  continue  for five (5) business  days
          after the  receipt of written  notice  that the  Company is in default
          hereunder; or

               b. Any of the  representations  or warranties made by the Company
          herein,  in  the  Subscription  Agreement,  or in any  certificate  or
          financial  or  other  written   statements   heretofore  or  hereafter
          furnished  by or on  behalf  of the  Company  in  connection  with the
          execution and delivery of this Debenture or the Subscription Agreement
          shall be false or misleading in any material respect at the time made;
          or

               c. The Company shall fail to perform or observe,  in any material
          respect, any other covenant, term, provision,  condition, agreement or
          obligation  of  the  Company  under  this  Debenture,   or  under  the
          Subscription  Agreement,  or under any related agreement, or under any
          document or instrument  granting security for amounts owing under this
          Debenture  including,  without  limitation,  any of the Loan Documents
          (defined below),  and such failure shall continue uncured for a period
          of five (5) business days after the receipt of written notice that the
          Company is in default  hereunder (it being understood that in the case
          of defaults which can not reasonably be cured within a 5-day period no
          grace period shall be  necessary as a  precondition  to the failure to
          perform such covenant constituting an Event of Default); or

               d. The Company  shall (1) make an  assignment  for the benefit of
          creditors or commence  proceedings for its  dissolution;  or (2) apply
          for or consent to the appointment of a trustee, liquidator or receiver
          for its or for a substantial part of its property or business; or


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<PAGE>


               e. A trustee,  liquidator or receiver  shall be appointed for the
          Company or for a substantial  part of its property or business without
          its consent and shall not be  discharged  within sixty (60) days after
          such appointment; or

               f.   Bankruptcy,   reorganization,   insolvency  or   liquidation
          proceedings or other  proceedings  for relief under any bankruptcy law
          or any law for the relief of debtors shall be instituted by or against
          the Company  and, if  instituted  against  the  Company,  shall not be
          dismissed within sixty (60) days after such institution or the Company
          shall by any action or answer  approve of, consent to, or acquiesce in
          any such  proceeding or admit the material  allegations of, or default
          in answering a petition filed in any such proceeding; or

               g. The Company shall fail to make any required material payments,
          fees, taxes, costs,  insurance premiums when due beyond any applicable
          grace period; or

               h. The  Company  shall  default on the  payment  of any  material
          indebtedness for borrowed money beyond any applicable grace period; or

               i. Any judgment, levy or attachment shall be rendered against the
          Company or any of its assets or  properties  in an amount in excess of
          $100,000 and such judgment, levy or attachment shall not be dismissed,
          stayed,  bonded or  discharge  within  thirty (30) days of the date of
          entry thereof; or

               j. The purified  phosphoric  acid facility  (the "PPA  Facility")
          owned by the  Company  in  Calgary  is not  fully  operational  within
          eighteen (18) months of the issuance of the Debentures; or

               k. The control of the Company or ESI  Resources  Limited or Earth
          Sciences  Extraction  Company  is  changed  by  reason  of  merger  or
          acquisition of shares of either company,  or sale of substantially all
          assets of either company; or

               l. The Company allows any of the following conditions without the
          prior written waiver of the Holder:

                    i. the  declaration  of a dividend  to holders of the Common
                    Stock;

                    ii. capital  expenditures,  except for the completion of the
                    PPA Facility, in any calendar quarter exceeding $500,000; or

                    iii.  consolidated  working capital at any calendar  quarter
                    end  date,  irrespective  of this or any  other  convertible
                    debenture, of less than $500,000.


Upon the  occurrence of any Event of Default or at any time  thereafter,  and in
each and every such case, unless such Event of Default shall have been waived in
writing by the Holder  (which  waiver  shall not be deemed to be a waiver of any
subsequent  Event of  Default)  at the option of the Holder and in the  Holder's
sole discretion,  then or at any time  thereafter,  at the option of the Holder,
the whole of said principal sum then remaining unpaid  hereunder,  together with
all interest  accrued  thereon,  and all other sums owing hereunder or under the
Loan  Documents,  shall  immediately  become  due  and  payable  without  notice
("Acceleration") and the liens given to secure the payment of this Debenture may
be foreclosed and the Holder may pursue all rights and remedies  available under
this Debenture, or under the Loan Documents, or otherwise available at law or in
equity.

          6. Following the occurrence of an Event of Default, and so long as any
such Event of Default shall remain outstanding and uncured, the Company promises
to pay interest on the outstanding  principal balance of this Debenture,  and on
any and all other amounts then outstanding,  at a rate of interest (the "Default
Rate") equal to the greater of (i) eighteen percent (18%) per annum or (ii) five
percent (5%) per annum in excess of the prime interest rate of Bank One, Denver,
Colorado in effect at the time ("Prime  +5%"),  provided that any interest which
has accrued at the Default Rate shall be paid at the time of, and as a condition
precedent to the curing of any default  under any statutory  right to cure.  The
fluctuating   Default  Rate  at  which   interest   accrues  shall  be  adjusted
simultaneously,  at each announced change of the Prime Rate. Failure to exercise
such option or charge of such  increased  interest  shall not be a waiver of the
right to do so at any future time or with respect to any other default.

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<PAGE>



         7. No provision of this Debenture  shall alter or impair the obligation
of the Company which is absolute and unconditional, to pay the principal of, and
interest on, this  Debenture at the time,  place,  and rate,  and in the coin or
currency,  herein  prescribed.  This  Debenture and all other  Debentures now or
hereafter  issued of similar terms are direct  obligations  of the Company.  The
Company shall pay all costs and expenses,  including reasonable attorneys' fees,
which the  Holder may incur in  connection  with any effort or action to collect
amounts due under this Debenture.

          8. No recourse  shall be had for the payment of the  principal  of, or
the interest on, this Debenture,  or for any claim based hereon, or otherwise in
respect hereof, against any incorporator,  shareholder,  officer or director, as
such,  past,  present or future,  of the Company or any  successor  corporation,
whether  by  virtue  of any  constitution,  statue  or rule  of  law,  or by the
enforcement of any assessment or penalty or otherwise, all such liability being,
by the acceptance  hereof and as part of the consideration for the issue hereof,
expressly waived and released.

          9. The rights or remedies of the Holder as provided in this  Debenture
and the Loan  Documents  shall be cumulative  and  concurrent and may be pursued
singly, successively, or together against the Company, the property described in
the Loan Documents, and any other funds, property or security held by the Holder
for the payment  hereof or otherwise at the sole  discretion of the Holder.  The
failure to exercise any such right or remedy shall in no event be  considered as
a waiver or release of such rights or remedies or the right to exercise  them at
any later time.

          10. In the  event  the  interest  provisions  hereof or any  exactions
provided for herein,  or in the Loan Documents or any other instrument  securing
this Debenture shall result,  because of any reduction of principal,  or for any
reason  at any time  during  the life of this  loan,  in any  effective  rate of
interest  which,  for any month,  transcends the limit of the usury or any other
law applicable to the obligation  evidenced hereby,  all sums in excess of those
lawfully  collectible  as  interest  for the period in question  shall,  without
further  agreement  or notice  between or by any party  hereto,  be applied upon
principal immediately upon receipt of such moneys by Holder, with the same force
and effect as though the payor had specifically designated such extra sums to be
so applied to principal  and Holder had agreed to accept such extra payment as a
premium-free  prepayment.  In no event shall any agreed to or actual exaction as
consideration  for this  obligation  transcend the limits imposed or provided by
the  laws  applicable  to  this   transaction  or  the  Company  hereof  in  the
jurisdiction  in which any of the  security  herefor is  located  for the use or
detention of money or for forbearance in seeking its collection.

          11. The Company and all  endorsers,  guarantors and all persons liable
or to become liable on this  Debenture  waive  presentment,  protest and demand,
notice of protest,  demand and dishonor and  nonpayment of this  Debenture,  and
consent to any and all renewals and  extensions  in the time of payment  hereof,
and agree,  further,  that at any time and from time to time without notice, the
terms of payment  herein may be modified or the  security  described in the Loan
Documents  released in whole or in part or  increased,  changed or  exchanged by
agreement  between the Holder  hereof and any owner of the property  affected by
said Loan Documents  without in anywise  affecting the liability of any party to
this  instrument  or any person  liable or to become  liable with respect to any
indebtedness  evidenced  hereby.  The  right to  plead  any and all  statues  of
limitation as a defense to any demand on this Debenture, or any guaranty hereof,
or any agreement to pay the same, or any demand  secured by the Loan  Documents,
or any and all  obligations or liabilities  arising out of or in connection with
this Debenture or in the Loan Documents,  is expressly  waived by each and every
of the Company, endorsers, or guarantors to the fullest extent permitted by law.


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<PAGE>


          12.  Any  forbearance  of  Holder  in  exercising  any right or remedy
hereunder or under the Loan Documents, or otherwise, afforded by applicable law,
shall not be a waiver of or preclude  the  exercise of any right or remedy.  The
acceptance by Holder of payment of any sum payable, hereunder after the due date
of such payment shall not be a waiver of Holder's right to either require prompt
payment when due of all other sums payable hereunder or to declare a default for
failure  to make  prompt  payment.  Holder  shall at all times have the right to
proceed  against any portion of the  security  held herefor in such order and in
such manner as Holder may deem fit,  without  waiving any rights with respect to
any other security. No delay or omission on the part of Holder in exercising any
right  hereunder  shall  operate as a waiver of such right or of any other right
under this Debenture.

          13. This  Debenture  shall be governed by and  construed in accordance
with the laws of the  State of  Colorado  without  regard  to the  choice of law
provisions  thereof,  and in the event this  Debenture is placed in the hands of
any attorney for collection or is collected through any legal  proceedings,  the
undersigned  promises to pay (in addition to costs and  disbursements  otherwise
allowed),  to the extent permitted by law,  reasonable  attorneys' fee and legal
costs  (whether  or not  suit  is  commenced  and  whether  or not  incurred  in
connection  with appeal of a lower court  judgment or order or in collecting any
judgment entered  therein),  and if foreclosure is made by the Public Trustee or
any other public official,  reasonable  attorneys' fees and legal costs shall be
added by the Public Trustee or such public  official to the cost of foreclosure.
The  undersigned  hereby  represents  that the proceeds of the loan evidenced by
this Debenture will be used for a commercial or business purpose.

          14.  Time is of the  essence  with  regard to the  performance  of the
obligations of the Company in this  Debenture and each and every term,  covenant
and condition herein by or applicable to the Company.

          15.  This  Debenture  is  guaranteed  by a  guarantee  executed by ESI
Resources Limited, a wholly-owned subsidiary of the Company ("ESI Guaranty") and
the ESI Guaranty is secured by that  certain  security  agreement,  of even date
herewith,  encumbering  certain  equipment  and fixtures  located at the solvent
extraction  plant  in  Calgary,   Alberta  Canada  (the  "ESI  Calgary  Security
Agreement").  And, this Debenture is guaranteed by a guarantee executed by Earth
Sciences Extraction Company, a partnership in which ESI Resources Limited is the
general  partner ("ES  Extraction  Guaranty") and the ES Extraction  Guaranty is
secured by that certain security agreement,  of even date herewith,  encumbering
certain  equipment  and  fixtures  located at the  solvent  extraction  plant in
Calgary, Alberta Canada (the "ES Extraction Security Agreement"), and a security
agreement by the Company (the "ESI Security Agreement").

          16. This Debenture is secured by certain real and personal property in
the United States and Canada as set forth in that certain deed of trust, of even
date  herewith,  encumbering  real  property in Costilla  County,  Colorado (the
"Colorado  Deed of Trust"),  and in other  documents  and  instruments  given as
further  security  herefor  ( the  Colorado  Deed of  Trust,  ESI  Guaranty,  ES
Extraction  Guaranty,  ESI Calgary Security  Agreement,  ES Extraction  Security
Agreement,  ESI Security  Agreement and all such other security  documents being
collectively referred to herein as the "Loan Documents").

          17. The Company  hereby  irrevocably  waives,  to the  fullest  extent
permitted  by law,  any and all right to trial by jury in any  legal  proceeding
arising out of or relating to this Debenture and the other Loan Documents or the
transactions contemplated thereby. In any action which may be brought under this
Debenture,  Holder hereby irrevocably  consents to the personal  jurisdiction of
any State District Court or Federal Court located in the State of Colorado,  and
further  stipulates  and  agrees  that  venue  shall be  proper  in the State of
Colorado  for  any  such  actions  (save  and  except  for  the  foreclosure  or
enforcement of the ESI Guaranty,  ES Extraction  Guaranty,  ESI Calgary Security
Agreement,  ES Extraction  Security  Agreement,  and ESI Security  Agreement for
which venue shall be proper in the  province of Alberta in the City of Calgary),
and further  agrees not to seek a change of venue to any court outside the State
of Colorado without the consent of Holder.

          IN WITNESS WHEREOF,  the Company has caused this instrument to be duly
executed by an officer thereunto duly authorized.

                                              EARTH SCIENCES, INC.



                                              By:/s/ Mark H. McKinnies
                                              ------------------------
                                              Name:  Mark H. McKinnies
                                              Title:  President

Dated:  June 12, 1997


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<PAGE>



                                   EXHIBIT A

                              NOTICE OF CONVERSION

                    (To be Executed by the Registered Holder
                       in order to Convert the Debenture)


     The undersigned  hereby  irrevocably  elects to convert the above Debenture
No._____ into shares of Common Stock of EARTH  SCIENCES,  INC.  (the  "Company")
according to the conditions hereof, as of the date written below.



                                                --------------------------------
                                                Date of Conversion




                                                --------------------------------
                                                Applicable Conversion Price



                                                [SUBSCRIBER]




                                                 -------------------------------
                                                 Signature



                                                 Address:


                                                 -------------------------------


                                                 -------------------------------

*    The original  Debenture  and Notice of  Conversion  must be received by the
     Company by the third business day following the Date of Conversion.


                                       25