NioCorp SPAC Presentation Deck

Disclaimers & Technical Disclosures Legal Disclaimers This investor presentation (this "Presentation") is dated as of September 26, 2022 and contains information NioCorp Developments Ltd. ("NioCorp" or the "Company") (TSX: NB; OTCQX: NIOBF) and GX Acquisition Corp II ("GXII") (Nasdaq: GXII). This Presentation has been provided for informational purposes to assist recipients in deciding whether they wish to proceed in connection with possible business combination (the "Transaction") involving the Company and GXII and may not be used for any other purpose. This Presentation does not and, if hereafter supplemented, will not be all inclusive or contain all of the information that may be required to evaluate the Transaction or any investment in NioCorp or GXII. You should not rely upon it or use it to form the basis for any decision, contract, commitment or action whatsoever, with respect to any proposed transaction or otherwise. You should consult your own legal, regulatory, tax, business, financial and accounting advisors to the extent you deem necessary, and you must make your own investment decision and perform your own independent investigation and analysis of an investment in NioCorp or GXII and the Transaction contemplated in this Presentation. To the fullest extent permitted by law, in no circumstances will NioCorp, GXII, or any of their respective affiliates, officers, directors, employees, representatives, advisors or agents be responsible or liable for any direct, indirect or consequential loss or loss of profit arising from the use of this Presentation, its contents, its omissions, reliance on the information contained within it or on opinions communicated in relation thereto or otherwise arising in connection therewith. This Presentation and the analyses contained in it have been based, in part, certain assumptions and information obtained from industry studies and other sources. The use of such assumptions and information does not imply that NioCorp or GXII have independently verified, will verify or necessarily agree with any of such assumptions or information, and NioCorp and GXII have assumed and relied upon the accuracy and completeness of such assumptions and information for purposes of this Presentation. Neither NioCorp or GXII nor any of their respective affiliates, or their respective officers, directors, employees, representatives, advisors or agents, make any representation or warranty, express or implied, relation to the accuracy or completeness of the information contained in this Presentation or any oral information provided in connection herewith, or any data it generates, or that any transaction has been or may be effected on the terms or in the manner stated or implied by this Presentation, or as to the achievement or reasonableness of future projections, management targets, estimates, prospects or returns, if any, and accept no responsibility, obligation or liability (whether direct or indirect, in contract, tort or otherwise) in relation to any of such information. NioCorp, GXII and their respective affiliates, officers, directors, employees, representatives, advisors and agents expressly disclaim any and all liability which may be based on this Presentation and any errors therein or omissions therefrom. NioCorp and GXII own or have rights to various trademarks, service marks and trade names that they use in connection with the operation of their respective businesses. This Presentation may also contain trademarks, service marks, trade names and copyrights of other parties, which are the property of their respective owners. The use or display of third parties' trademarks, service marks, trade names or products in this Presentation is not intended to, and does not imply, a relationship with NioCorp or GXII, or an endorsement or sponsorship by or of NioCorp or GXII. Solely for convenience, some of the trademarks, service marks, trade names and copyrights referred to in this Presentation may be listed without the TM, SMⒸ or ® symbols, but such references are not intended to indicate, in any way, that NioCorp or GXII will not assert, to the fullest extent under applicable law, their rights or the rights of the applicable owners, if any, to these trademarks, service marks, trade names and copyrights. You should not construe the contents of this Presentation as legal, regulatory, tax, accounting or investment advice or a recommendation. We recommend that you seek independent third-party legal, regulatory, accounting and tax advice regarding the contents of this Presentation. This Presentation does not constitute and should not be considered as any form of financial opinion or recommendation by NioCorp, GXII or any of their respective affiliates. This Presentation is not a research report. By accepting this Presentation, you confirm that you are not relying upon the information contained herein to make any decision. NEITHER THE U.S. SECURITIES AND EXCHANGE COMMISSION ("SEC") NOR ANY STATE OR TERRITORIAL SECURITIES COMMISSION HAS APPROVED OR DISAPPROVED OF ANY SECURITIES OR DETERMINED IF THIS PRESENTATION IS TRUTHFUL OR COMPLETE. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE. IN ADDITION, NO SECURITIES COMMISSION OR SIMILAR REGULATORY AUTHORITY IN CANADA HAS REVIEWED OR IN ANY WAY PASSED UPON THIS PRESENTATION OR THE MERITS OF ANY OF THE SECURITIES REFERRED TO HEREIN, AND ANY REPRESENTATION TO THE CONTRARY IS AN OFFENCE. Additional Information About the Proposed Transaction and Where to Find It In connection with the proposed Transaction, NioCorp intends to file a registration statement on Form S-4 (the "registration statement") with the SEC, which will include document that serves as a prospectus and proxy circular of NioCorp and a proxy statement of GXII, referred to as a "joint proxy statement/prospectus." The definitive joint proxy statement/prospectus will be filed with the SEC as part of the registration statement and, in the case of NioCorp, with the applicable Canadian securities regulatory authorities, and will be sent to all NioCorp shareholders and GXII stockholders as of the applicable record date to be established. Each of NioCorp and GXII may also file other relevant documents regarding the proposed Transaction with the SEC and, in the case of NioCorp, with the applicable Canadian securities regulatory authorities. BEFORE MAKING ANY VOTING OR INVESTMENT DECISION, INVESTORS AND SECURITY HOLDERS OF NIOCORP AND GXII ARE URGED TO READ THE REGISTRATION STATEMENT, THE DEFINITIVE JOINT PROXY STATEMENT/PROSPECTUS AND ALL OTHER RELEVANT DOCUMENTS FILED OR THAT WILL BE FILED WITH THE SEC AND, IN THE CASE OF NIOCORP, WITH THE APPLICABLE CANADIAN SECURITIES REGULATORY AUTHORITIES IN CONNECTION WITH THE PROPOSED TRANSACTION, INCLUDING ANY AMENDMENTS OR SUPPLEMENTS TO THESE DOCUMENTS, CAREFULLY AND IN THEIR ENTIRETY BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION. Investors and security holders will be able to obtain free copies of the registration statement and the joint proxy statement/prospectus (if and when available) and all other relevant documents that are filed or that will be filed with the SEC by NioCorp or GXII through the website maintained by the SEC at www.sec.gov. Investors and security holders will be able to obtain free copies of the joint proxy statement/prospectus (if and when available) and all other relevant documents that are filed or that will be filed with the applicable Canadian securities regulatory authorities by NioCorp through the website maintained by the Canadian Securities Administrators at www.sedar.com. The documents filed by NioCorp and GXII with the SEC and, in the case of NioCorp, with the applicable Canadian securities regulatory authorities also may be obtained by contacting NioCorp at 7000 South Yosemite, Suite 115, Centennial CO 80112, or by calling (720) 639-4650; or GXII at 1325 Avenue of the Americas, 28th Floor, New York, NY 10019, or by calling (212) 616-3700. Participants in the Solicitation NioCorp, GXII and certain of their respective directors, executive officers and other members of management and employees may, under SEC rules, be deemed to be participants in the solicitation of proxies from NioCorp's shareholders and GXII's stockholders in connection with the proposed Transaction. Information regarding the executive officers and directors of NioCorp is included in its management information and proxy circular for its 2021 annual general meeting of shareholders filed with the SEC and the applicable Canadian securities regulatory authorities on October 22, 2021. Information regarding the executive officers and directors of GXII is included in its Annual Report on Form 10-K for the year ended December 31, 2021, filed with the SEC on March 25, 2022. Additional information regarding the persons who may be deemed to be participants in the solicitation, including information regarding their interests in the proposed Transaction, will be contained in the registration statement and the joint proxy statement/prospectus (if and when available). NioCorp's shareholders stockholders and other interested parties may obtain free copies of these documents free of charge by directing a written request to NioCorp or GXII. NioCorp Critical Mineral Security