Document:

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Exhibit 10.1
MINING LEASE

                                 LEASE AGREEMENT

Nevada Mine Properties II, Inc. (NMP or Lessor) agrees to lease to Pacific
Spirit Inc. (Lessee) the unpatented lode mining claims attach as Exhibit "A",
located in portions of sections 29, 30, and 31, T 31 N, R 38 E, MDB&M, Pershing
County, Nevada (referred to as property), subject to the following conditions:

Recitals:

A.   "Effective Date" means June 7, 2001.

B.   "Lease Year" means each one (1) year period following the Effective Date
     and each anniversary of the Effective Date.

C.   WARRANTIES. The Lessor warrants that he is the owner of the lode mining
     claims more particularly described in Exhibit A and said claims are free
     from all liens and encumbrances.

D.   EXPLORATION AND DEVELOPMENT RIGHTS. Lessor will grant the Property to
     Lessee for the Lease period with the exclusive right to explore, develop,
     and mine the Property for gold, silver, and other valuable minerals.

E.   PERFORMANCE REQUIREMENTS / ASSUMPTION OF CLAIM MAINTENANCE. Under
     applicable Federal, State and County laws and regulations, Federal, State,
     and County annual mining claim maintenance or rental fees are required to
     be paid for the unpatented mining claims which constitute all or part of
     the Property, beginning with the annual assessment work period of September
     1, 2001 to September 1, 2002. Lessee shall timely and properly pay the
     Federal, State, and County annual mining claim maintenance or rental fees,
     and shall execute and record or file, as applicable, proof of payment of
     the Federal, State, and County annual mining maintenance or rental fees and
     of Lessor's intention to hold the unpatented mining claims which constitute
     the Property. If Lessee does not terminate this Lease before June 7 or any
     subsequent Lease Year, Lessee will be obligated either to pay the Federal,
     State, and Local annual mining claim maintenance or rental fees for the
     Property due that year or to reimburse Lessor for same.

F.   AREA OF INTEREST. Any additional claims located or acquired by the Lessee
     within one (1) mile from the exterior boundaries of the mining claims
     described in Exhibit "A" shall become a part of the leased property and
     shall be subject to the terms of this lease as of the Effective Date.

G.   SCHEDULE OF MINIMUM PAYMENTS. The Lessee shall pay to the Lessor minimum
     payments, which shall be advance payments of the Royalty, of US$5000.00
     (five thousand dollars) upon execution of this lease. The Lessee may extend
     this lease upon payment of the following:

          1.   Pay Lessor US$8,000.00 on or before the first anniversary of the
               execution of this lease.

          2.   Pay Lessor US$16,000.00 on or before the second anniversary of
               the execution of this lease.

          3.   Pay Lessor US$24,000.00 on or before the third anniversary of the
               execution of this lease.

          4.   Pay Lessor US$50, 000.00 on or before the fourth anniversary of
               the execution of this lease.

          5.   Each annual payment thereafter shall be US$50,000.00 plus an
               annual increase or decrease equivalent to the rate of inflation
               designated by the Consumer's Price Index (CPI) for that year with
               execution year as base year. Each such payment shall be made on
               or before the successive anniversary of the execution of this
               lease.

H.   BUYOUT. Buyout price is US$5,000,000 (five million dollars) from which
     advance royalty payments, made up to the day of the buyout, may be
     subtracted from the Buyout price. Lessee will pay Lessor a perpetual
     one-half per cent (0.5%) royalty on Net Smelter Returns (as defined below
     in Section I. of this document) thereafter.

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I.   DEFINITION OF NET SMELTER RETURNS. During the term of this Agreement,
     Lessee shall pay to Lessor, as a land owner's Production Royalty, a
     percentage of the Net Smelter Returns (as defined below) from the sale of
     any Valuable Minerals, Ore, and Product mined and sold from the Property.
     "Net Smelter Returns" are defined as the gross revenues actually received
     by the Lessee from the sales of any Valuable Minerals extracted and
     produced from the Property less the following charges:

     1.   All costs to Lessee of weighing, sampling, determining moisture
          content and packaging such material and of loading and transporting it
          to the point of sale, including insurance and in-transit security
          costs.

     2.   All smelter costs and all charges and penalties imposed by the
          smelter, refinery, or purchaser.

     3.   Marketing costs and commissions.

     4.   Not withstanding the foregoing, for purposes of determining the
          royalty payable to Lessor on any gold and/or silver produced from the
          Property, the price attributed to such gold and/or silver shall be the
          price per ounce of gold and/or silver on which the royalty is to be
          paid (as the case may be) as quoted on the London Metals Exchange at
          the PM fix on the day prior to the date of final settlement from the
          smelter, refinery or other buyer of the gold and/or silver on which
          the royalty is to be paid (the "Quoted Price"). For purposes of
          determining the gross revenues, in the event the Lessee elects not to
          sell any portion of the gold and/or silver mined from the Property,
          but instead elects to have the final product of any such gold and/or
          silver credited to be held for its account with any smelter, refiner,
          or broker, such gold and/or silver shall be deemed to have been sold
          at the Quoted Price on the day such gold and/or silver is actually
          credited to or placed in Lessee's account. The percentage for this
          Production Royalty shall be four per cent (4%).

     5.   Lessor shall be paid the Production Royalty quarterly by certified
          check by the Lessee.

J.   CONDITIONS OF TERMINATION BY LESSOR. This Lease may be terminated at any
     time by the Lessor subject to the following:

     1.   If Lessee fails to meet the above lease payments, Lessor must give
          written notice to Lessee of such default. After receipt of default,
          Lessee has 15 days to cure the default.

     2.   If Lessee fails to make Federal, State, and County maintenance
          payments or filing fees at least 15 days prior to due date, Lessee
          shall notify Lessor of a possible default. After 10 days, if the
          default is not cured Lessor may initiate payment on the claims. Lessee
          will be able to cure this default by reimbursing all Federal, State,
          and County Payments made by the Lessor plus a 20% penalty within 30
          days.

K.   CONDITIONS OF TERMINATION BY LESSEE. This Lease may be terminated at any
     time by the Lessee subject to the following:

     1.   Lessee must give written notice 30 days prior to relinquishing the
          leased property.

     2.   In the event Lessee desires to terminate the agreement after June1 of
          any year, Lessee shall be responsible for all Federal, State, and
          County maintenance and filing fees for the next assessment year
          regarding the leased property.

     3.   Lessee shall deliver to Lessor, in reproducible form, all data
          generated or obtained for the leased property, whether factual or
          interpretive as defined in section P.

     4.   Lessee shall quitclaim to Lessors all claims located or acquired by
          Lessee within one (1) mile area of interest described in section F.

L.   RECLAMATION, COMPLIANCE WITH THE LAW. All exploration and development work
     performed by the Lessee during the term of this Agreement shall conform
     with the applicable laws and regulations of the state in which the Property
     is situated and of the United States of America. Lessee shall be fully
     responsible for compliance with all applicable Federal, State, and local
     reclamation statutes, regulations, and ordinances relating to such work, at
     Lessee's cost, and Lessee shall indemnify and hold harmless Lessor from any
     and all claims, assessments, fines, and actions arising from Lessee's
     failure to perform the foregoing obligations. Lessee's reclamation
     obligation shall survive termination of the Agreement. Lessor agrees to
     cooperate with Lessee in Lessee's application for governmental licenses,

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     permits, and approvals, the costs of which shall be borne by Lessee. Lessee
     shall own all governmental licenses, permits, and approvals.

M.   LIENS. Lessee shall keep the property free from any and all liens and
     encumbrances.

N.   TRANSFER, ASSIGNMENT, RIGHT OF FIRST REFUSAL. Either party shall be free to
     assign its rights under the detailed agreement to an affiliate company.
     They also shall have the right to transfer all or part of their interest in
     the Agreement to a third party, but transfers to a third party shall be
     subject to a right of first refusal by the Lessor. Assignments permitted
     under this paragraph shall not be effective unless and until the permitted
     assignee agrees in writing in form and substance acceptable to the
     remaining party assuming all of the assigning party's obligations under
     this Lease Agreement. The party assigning interest in this lease shall
     notify the other party within 15 days of such assignment and all parts of
     this agreement will remain in effect.

O.   LEASE TERM. The term of this lease is for thirty (30) years, renewable for
     an additional thirty (30) years so long as conditions of the lease are met.

P.   DATA AND REPORTS. Upon and after execution of the detailed agreement,
     Lessor will make available to Lessee all technical data, survey notes or
     maps, samples, drilling results including drill logs and reports concerning
     the Property which Lessor possesses, or to which it has access, of which it
     acquires in the future. Within 60 days after termination of the detailed
     agreement, Lessee shall return to Lessor all information of a nature
     similar to that described above and developed by Lessee during the term of
     the Mining Lease. If requested by Lessor not more than once in any 12
     calendar months, Lessee shall submit to Lessor, within 60 days of Lessee's
     receipt of such request, an annual progress report describing Lessee's work
     upon the Property, the results of such work, and the amounts expended by
     Lessee in furtherance thereof to the date of such report.

Q.   NOTIFICATION TO LESSOR. All notices and payments from Lessee to Lessor
     shall be sent to:

                  NEVADA MINE PROPERTIES II, Inc.
                  Attn.  Mr. John Prochnau
                  127 Cheney St.
                  Reno, NV.  89501    USA

     or any other person Lessor shall designate. If Lessor designates an
     alternative person to receive notices and payment, they shall provide
     written notice of such to Lessee. All lease payments shall be made in the
     form of a check payable to Nevada Mine Properties II, Inc.

R.   NOTIFICATION TO LESSEE. All notices from Lessor to Lessee shall be sent to:

                  Pacific Spirit Inc.
                  Attn. Peter Sotola, President
                  11640 - 96 A Avenue
                  Vancouver, BC   V3V 2A1
                  Canada

     or any other person Lessee shall designate. If Lessee designates an
     alternative person to receive notices, they shall provide written notice of
     such to Lessor.

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The parties have executed this Lease Agreement effective as of the Effective
Date.

NEVADA MINE PROPERTIES II, INC.

By /s/ George Elispulos

Title Secretary

Personally appeared before me George Elispulos with whom I am personally
acquainted (or proved to me on the basis of satisfactory evidence) and who
acknowledged that he executed the within instrument for the purposes therein
contained.

Witness my hand, at office, this 22nd day of May, 2001.

[SEAL]

/s/ Patrick MacMullen

NOTARY PUBLIC

PACIFIC SPIRIT INC.

By /s/ Peter Sotola

Title President

Personally appeared before me Peter Sotola with whom I am personally acquainted
(or proved to me on the basis of satisfactory evidence) and who acknowledged
that he executed the within instrument for the purpose therein contained.

Witness my hand, at office, this 7th day of June, 2001.

/s/ Lee Seifert

NOTARY PUBLIC
[SEAL]

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                                                    EXHIBIT "A"

CLAIM NAMES                         BLM SERIAL NUMBERS
-----------                         ------------------
DEL ORO #3                                  NMC 556966
DEL ORO #70                                 NMC 398101
DEL ORO #73                                 NMC 398104
NP #127                                     NMC 724576
NP #129                                     NMC 724578
NP #133                                     NMC 724582<Page>

                           PURCHASE AND SALE AGREEMENT

                                 BY AND BETWEEN

                             KEYSTONE PROPERTY TRUST
                                  (as "Buyer")

                                       AND

                       RECKSON OPERATING PARTNERSHIP, L.P.
                                       and
                        RECKSON CONSTRUCTION GROUP, INC.
                                 (as "Sellers")

                           DATED AS OF AUGUST 21, 2001

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         PURCHASE AND SALE AGREEMENT, dated as of August 21, 2001 (the
"Agreement") by and between Reckson Operating Partnership, L.P., a Delaware
limited partnership ("ROP"), and Reckson Construction Group, Inc., a New York
corporation ("RCG," and together with ROP, the "Sellers") and Keystone Property
Trust, a Maryland real estate investment trust (the "Buyer").

         WHEREAS, the Sellers desire to sell and transfer to Buyer 2,500,000
common shares of beneficial interest to be received by the Sellers (the "Common
Shares") upon conversion and/or exchange of the securities described on EXHIBIT
A hereto (the "Securities") and Buyer wishes to acquire the Common Shares on the
terms set forth in this Agreement; and

         WHEREAS, the conversion and/or exchange of the Securities into the
Common Shares shall occur immediately prior to the Closing (as defined below) of
the Common Shares on the Closing Date (as defined below).

         THEREFORE, the parties hereto agree as follows:

         1. SALE AND PURCHASE OF THE SECURITIES. Each Seller hereby agrees to
assign, sell, convey and transfer to Buyer on the Closing Date (as defined
below) all right, title and interest of such Seller in and to the respective
number of Common Shares to be received by such Seller upon conversion and/or
exchange of the Securities set forth opposite such Seller's name on EXHIBIT A
hereto and Buyer, in reliance on the representations and warranties set forth
herein, agrees to pay to such Seller the respective amount of the Purchase
Price (as defined herein) in respect of such sale as set forth opposite such
Seller's name on EXHIBIT A hereto. The Common Shares shall be free and clear
of all liens, pledges, claims, security interests, encumbrances, charges,
restrictions or limitations of any kind, whether arising by agreement,
operation of law or otherwise (collectively, "Liens"). On the Closing Date
and pursuant to instructions from American Stock Transfer & Trust Company,
each of the Sellers and Buyer shall instruct American Stock Transfer & Trust
Company to record the transfer to the Buyer of the uncertificated Common
Shares owned by the Sellers after conversion of the Securities.

         2. CLOSING. The closing of the purchase and sale of the Common
Shares (the "Closing") shall take place on August 27, 2001 and the Sellers
will assign, sell, convey and transfer to Buyer in accordance with Section 1
above all right, title and interest of Sellers in and to the Common Shares
for an aggregate purchase price of $35,700,000 (the "Purchase Price"). Buyer
shall pay to each Seller, in accordance with EXHIBIT A, such Seller's
respective amount of the Purchase Price in immediately available funds by
wire transfer on the Closing Date to an account designated by the respective
Seller in writing at least two business days prior to the Closing Date.

         3. REPRESENTATIONS AND WARRANTIES OF SELLERS. Each Seller hereby
represents and warrants to Buyer that each of the following statements is
true and correct as of the date hereof and will be true and correct as of the
Closing Date as if made on such date.

         (a) GOOD STANDING. Seller is duly organized, validly existing and in
good standing in the state of its organization, with full corporate or
partnership power, as applicable, and authority to carry on its business as
it is now operated and carried on by it.
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         (b) DUE AUTHORIZATION. Seller has all requisite corporate or
partnership power, as applicable, and authority to execute and deliver this
Agreement and to perform its obligations hereunder and to consummate the
transactions contemplated hereby. This Agreement has been duly authorized,
executed and delivered by Seller and constitutes a valid and binding
agreement of Seller enforceable against Seller in accordance with its terms.

         (c) ABSENCE OF DEFAULTS AND CONFLICTS. The execution, delivery and
performance of this Agreement by Seller and the consummation of the
transactions contemplated hereby do not and will not violate or be in
conflict with, or constitute a breach of or default (or an event which, with
notice or lapse of time or both, would constitute a default) under the terms
of any law, regulation, order, judgment, instrument, contract, license or
other agreement to which Seller is a party or by which Seller or its assets
are bound or which would prevent the consummation of this transaction, and no
consent or approval of any third party or any government, state, province,
county or other political subdivision thereof, or any entity exercising
executive, legislative, judicial, regulatory or administrative function of,
or pertaining to, governing (collectively, "Governmental Authority") is
necessary in order to permit Seller to execute and deliver this Agreement and
perform the transactions contemplated hereby.

         (d) TITLE TO INTEREST. Prior to the conversion and/or exchange of
the Securities into the Common Shares, the Seller has not sold, transferred,
pledged or otherwise disposed of, or converted or exchanged, or granted any
option or other right with respect to, any of the Securities and Seller has
good and marketable title to the Securities free and clear of all Liens. Upon
conversion of the Securities into the Common Shares, Seller will have good
and marketable title to the Common Shares, Seller will not have sold,
transferred, pledged or otherwise disposed of, or converted or exchanged, or
granted any option or other right with respect to the Common Shares and
Seller will convey to Buyer good, valid and marketable title to the Common
Shares free and clear of all Liens.

         (e) BROKERS. Seller has not employed any broker or finder or
incurred any liability for any brokerage fees or commissions in connection
with the transactions contemplated by this Agreement.

         (f) LITIGATION. There is no suit, claim, action, proceeding or
investigation pending or, to the Seller's knowledge, threatened against the
Seller or its affiliates or any of their predecessors with respect to the
Securities at law or in equity or before any Governmental Authority or before
any arbitrator of any kind and, to the Seller's knowledge, there is no
reasonable basis for any such suit, claim, action, proceeding or
investigation. The Seller has not been a party to any such suit, claim,
action, proceeding or investigation during the past two years relating to the
Securities, nor has any such suit, claim, action, proceeding or investigation
been threatened in writing by or against the Seller.

                                       2
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         (g) REGULATION M. Seller acknowledges that neither the Buyer nor any
of its agents or affiliates solicited the sale of the Securities by Seller
and that the transactions contemplated hereby qualify as an "unsolicited
purchase" under Rule 102 of Regulation M promulgated under the rules and
regulations of the Securities Act of 1933, as amended.

         4. REPRESENTATIONS AND WARRANTIES OF BUYER. Buyer hereby represents
and warrants to each Seller that each of the following statements is true and
correct as of the date hereof and will be true and correct as of the Closing
Date as if made on such date.

         (a) GOOD STANDING AND DUE AUTHORIZATION. Buyer is duly organized,
validly existing and in good standing in the state of its incorporation, with
full trust power and authority to carry on its business as it is now operated
and carried on by it. Buyer has all requisite trust power and authority to
execute and deliver this Agreement and to perform its obligations hereunder
and to consummate the transactions contemplated hereby. This Agreement has
been duly authorized, executed and delivered by Buyer and constitutes a valid
and binding agreement of Buyer enforceable against Buyer in accordance with
its terms.

         (b) ABSENCE OF DEFAULTS AND CONFLICTS. The execution, delivery and
performance of this Agreement by Buyer and the consummation of the
transactions contemplated hereby do not and will not violate or be in
conflict with, or constitute a breach of or default (or an event which, with
notice or lapse of time or both, would constitute a default) under the terms
of any law, regulation, order, judgment, instrument, contract, license or
other agreement to which Buyer is a party or by which Buyer or its assets are
bound or which would prevent the consummation of this transaction, and no
consent or approval of any Governmental Authority is necessary in order to
permit Buyer to execute and deliver this Agreement and perform the
transactions contemplated hereby.

         (c) BROKERS. Buyer has not employed any broker or finder or incurred
any liability for any brokerage fees or commissions in connection with the
transactions contemplated by this Agreement.

         5. COVENANTS.

         (a) From the date hereof until the Closing Date, each Seller will
not, and will direct its employees, agents and other representatives
(including, without limitation, any financial advisor, attorney or accountant
retained by such Seller) not to, directly or indirectly, solicit, encourage,
or participate in any way in discussions or negotiations with, or provide any
information, data or assistance to, any third party (other than Buyer and its
affiliates) concerning any acquisition of, or other transaction involving,
the Securities. Each Seller will promptly communicate to Buyer in writing the
terms of any proposal or contact it may receive in respect of any such
transaction.

         (b) Each party to this Agreement shall execute and deliver, or cause
to be executed and delivered, all such instruments and shall take all such
actions as the other party may reasonably request in order to effect the
intent and purposes of and to carry out the terms of this Agreement.

         (c) Each Seller shall give Buyer and its authorized representatives,
at all reasonable times during regular business hours and on reasonable
advance notice, access to all information

                                       3
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reasonably available to it which is necessary to Buyer to enable Buyer to
evaluate the merits and risks of purchasing the Securities.

         (d) Each Seller shall not sell, transfer, pledge or otherwise
dispose of, or convert or exchange, or grant any option or other right with
respect to, any of the Securities.

         6. SURVIVAL OF REPRESENTATIONS AND WARRANTIES. All representations
and warranties contained or made in, or in connection with, this Agreement
shall survive the purchase and sale of the Common Shares, notwithstanding any
investigation conducted with respect thereto or any knowledge acquired as to
the accuracy or inaccuracy of any such representation or warranty.

         7. INDEMNIFICATION.

         (a) Each Seller, jointly and severally, agrees to defend, indemnify
and hold harmless Buyer, and its trustees, officers, employees, agents and
any of their successors and assigns, from and against any and all losses,
damages, claims, suits, proceedings, liabilities, costs and expenses
(including settlement costs, interest, penalties, reasonable attorney's fees
and any reasonable legal or other expenses for investigation or defense of
any actions or threatened actions) (collectively, "Losses" or "Claims," as
the context requires) which may be imposed, sustained, incurred or suffered
or asserted as a result of, relating to or arising out of (i) the breach of
any representation or warranty of such Seller contained in this Agreement;
(ii) any failure by such Seller to perform any covenant, agreement or
obligation of Seller contained in this Agreement; and (iii) such Seller's
ownership of the Securities prior to the Closing Date, including liabilities
for taxes, charges, fees and periodic deposits (including interest and
penalties) determined to have been due to any Governmental Authority during
the period that such Seller owned or held the Securities.

         (b) Buyer agrees to defend, indemnify and hold harmless each Seller
and its partners, officers, directors, employees, agents and any of their
successors and assigns from and against any and all Losses or Claims which
may be imposed, sustained, incurred or suffered or asserted as a result of,
relating to or arising out of (i) the breach of any representation or
warranty of Buyer contained in this Agreement; and (ii) any failure by Buyer
to perform any covenant, agreement or obligation of Buyer contained in this
Agreement.

         8. CONFIDENTIALITY. All information furnished in writing by one
party to this Agreement to another party to this Agreement in connection with
this Agreement and the transactions contemplated hereby shall be kept
confidential by the receiving party and shall be used by the receiving party
only in connection with this Agreement and the transactions contemplated
hereby, except to the extent that such information (i) is information which
the receiving party can demonstrate was already known to the receiving party
when received; (ii) thereafter becomes lawfully obtainable from other sources
through no act or failure to act on the part of the receiving party; or (iii)
is required to be disclosed pursuant to applicable law, rules or regulations
(including the Securities Exchange Act of 1934, as amended and the rules and
regulations thereunder or the rules of any stock exchange), provided, that
the receiving party shall disclose only so much of the confidential
information as is legally required.

                                       4
<Page>

         9. MISCELLANEOUS.

         (a) All fees and expenses incurred in connection with this Agreement
and the transactions contemplated hereby, including all fees of counsel and
accountants, shall be paid by the party incurring the same.

         (b) This agreement may be terminated by the Sellers and the
transactions contemplated by it abandoned by notice from the Sellers to Buyer
if the Closing does not occur on the Closing Date, provided, however, that
the right to terminate this Agreement shall not be available if the Sellers'
breach of this Agreement has been the cause of the failure of the Closing to
occur on the Closing Date.

         (c) All notices, requests, demands and other communications required
or permitted under this Agreement shall be in writing and shall be delivered
personally, sent facsimile transmission, or sent next-day delivery via
Federal Express or a similar overnight courier. All communications to the
Sellers hereunder should be sent to Reckson Associates Realty Corp., 225
Broadhollow Road, Melville, New York 11747, Attn: Scott H. Rechler,
telephone: (631) 694-6900, facsimile: (631) 622-6788, with a copy to J.
Gerard Cummins, Sidley Austin Brown & Wood LLP, One World Trade Center, New
York, New York 10048, telephone: (212) 839-5300, facsimile: (212) 839-5599 or
to such other person or address as the Seller shall furnish to Buyer in
writing. All communications to Buyer hereunder should be sent to Keystone
Property Trust, 200 Four Falls Corporate Center, Suite 208, West
Conshohocken, Pennsylvania 19428, Attn: General Counsel, telephone: (484)
530-1800, facsimile: (484) 530-0131, with a copy to Clifford Chance Rogers &
Wells LLP, 200 Park Avenue, New York, NY 10166, Attn: Robert E. King, Jr.,
Esq., telephone: (212) 878-8000, facsimile: (212) 878-8375.

         A notice shall be deemed given for purposes of this Agreement (i) on
the date of delivery, if delivered personally or sent by facsimile transmission,
and (ii) on the first business day following the date of dispatch if sent
next-day delivery via Federal Express or similar a overnight courier. Any party
may change the address to which notices are to be sent by giving written notice
of such change of address to the other parties in the manner above provided for
giving notice.

         (d) THIS AGREEMENT SHALL BE CONSTRUED IN ACCORDANCE WITH AND
GOVERNED BY THE LAWS OF NEW YORK (WITHOUT GIVING EFFECT TO ANY CONFLICTS OR
CHOICE OF LAWS PROVISIONS THAT WOULD CAUSE THE APPLICATION OF THE DOMESTIC
SUBSTANTIVE LAWS OF ANY OTHER JURISDICTION).

         (e) This Agreement may not be amended, modified, superseded,
cancelled, renewed or extended except by a written instrument signed by both
Buyer and Seller; provided, that Buyer may assign its rights under this
Agreement to the Operating Partnership.

         (f) If any one or more of the covenants, agreements, provisions or
terms of this Agreement shall be held invalid, then such covenants,
agreements, provisions or terms shall be deemed severable from the remaining
covenants, agreements, provisions or terms of this Agreement and inoperative
to the extent it may conflict with any applicable statute or rule of law

                                       5
<Page>

and shall be deemed modified to conform with such statute or rule of law and
shall in no way affect the validity or enforceability of the other provisions
of this Agreement or the rights of the parties hereto.

         (g) This Agreement may be executed simultaneously in two or more
identical counterparts, each of which shall be deemed an original, but all of
which together shall constitute one and the same instrument.

         (h) EACH OF THE PARTIES HERETO HEREBY VOLUNTARILY AND IRREVOCABLY
WAIVES TRIAL BY JURY IN ANY ACTION OR OTHER PROCEEDING BROUGHT IN CONNECTION
WITH THIS AGREEMENT, ANY OF THE OTHER TRANSACTION DOCUMENTS OR ANY OF THE
TRANSACTIONS CONTEMPLATED HEREBY OR THEREBY.

         (i) Each party hereto further agrees that, at any time and from time
to time, upon the written request of the other party hereto, it will execute
and deliver such further instruments and do such further acts and things
reasonably necessary, desirable or proper as the requesting party may
reasonably request in order to effect the purposes of this Agreement.

                                       6
<Page>

         IN WITNESS WHEREOF, the parties have executed this Agreement, acting
their duly authorized agents, as of the date first above written.

                                       KEYSTONE PROPERTY TRUST

                                       By:
                                          --------------------------------------
                                          Name:  Robert F. Savage Jr.
                                          Title: Executive Vice President and
                                                 Chief Operating Officer

                                       RECKSON OPERATING PARTNERSHIP, L.P.

                                       By: Reckson Associates Realty Corp.,
                                           its general partner

                                       By:
                                          --------------------------------------
                                          Name:  Scott H. Rechler
                                          Title: Co-Chief Executive Officer

                                       RECKSON CONSTRUCTION GROUP, INC.

                                       By:
                                          --------------------------------------
                                          Name:  Gregg Rechler
                                          Title: President

                                       7
<Page>

                                                                       EXHIBIT A

<Table>
<Caption>

--------------------------------------------------------------------------------------------------------------------
          SELLER                                    SECURITIES                               PURCHASE PRICE
--------------------------------------------------------------------------------------------------------------------

<S>                              <C>                                                        <C>
Reckson Operating Partnership,   803,871 shares of 9.75% Series B Preferred Stock           $17,936,371.69
L.P.                             of Keystone Property Trust (to be converted into
                                 common shares of beneficial interest of Keystone
                                 Property Trust prior to the Closing Date); and

                                 296,795 9.75% Series C Preferred Units of Limited
                                 Partnership of Keystone Operating Partnership,
                                 L.P. (to be converted into common units of                  $6,622,238.44
                                 limited partnership of Keystone Operating
                                 Partnership, L.P. which will be exchanged into
                                 common shares of beneficial interest of Keystone
                                 Property Trust prior to the Closing Date).
--------------------------------------------------------------------------------------------------------------------

Reckson Construction Group,      499,334 9.75% Series C Preferred Units of Limited          $11,141,389.87
Inc.                             Partnership of Keystone Operating Partnership,
                                 L.P. (to be converted into common units of
                                 limited partnership of Keystone Operating
                                 Partnership, L.P. which will be exchanged into
                                 common shares of beneficial interest of Keystone
                                 Property Trust prior to the Closing Date).
--------------------------------------------------------------------------------------------------------------------
</Table>

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