Sec Form 3 Filing - MAINSAIL GP III, LLC @ Brilliant Earth Group, Inc. - 2021-09-23

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person MAINSAIL GP III, LLC 2. Issuer Name and Ticker or Trading Symbol Brilliant Earth Group, Inc. [ ?BRLT?] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O MAINSAIL MANAGEMENT COMPANY, LLC, 500 WEST 5TH STREET, SUITE 1100 3. Date of Earliest Transaction (MM/DD/YY) 09/23/2021 (Street) AUSTIN, TX78701 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Class B Common Stock 32,435,595 ( 1 ) I See footnote ( 2 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares LLC Units ( 1 ) ( 1 ) ( 1 ) Class A Common Stock 32,435,595 ( 1 ) I See footnote ( 2 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other MAINSAIL GP III, LLC C/O MAINSAIL MANAGEMENT COMPANY, LLC 500 WEST 5TH STREET, SUITE 1100 AUSTIN, TX78701 X Mainsail Partners III, L.P. C/O MAINSAIL MANAGEMENT COMPANY, LLC 500 WEST 5TH STREET, SUITE 1100 AUSTIN, TX78701 X MAINSAIL INCENTIVE PROGRAM, LLC C/O MAINSAIL MANAGEMENT COMPANY, LLC 500 WEST 5TH STREET, SUITE 1100 AUSTIN, TX78701 X Mainsail Co-Investors III, L.P. C/O MAINSAIL MANAGEMENT COMPANY, LLC 500 WEST 5TH STREET, SUITE 1100 AUSTIN, TX78701 X MAINSAIL MANAGEMENT COMPANY, LLC C/O MAINSAIL MANAGEMENT COMPANY, LLC 500 WEST 5TH STREET, SUITE 1100 AUSTIN, TX78701 X Signatures /s/ Gavin Turner, Mainsail GP III, LLC 09/23/2021 Signature of Reporting Person Date /s/ Gavin Turner, Mainsail Partners III, L.P. 09/23/2021 Signature of Reporting Person Date /s/Gavin Turner, Mainsail Co-Investors III, L.P. 09/23/2021 Signature of Reporting Person Date /s/ Gavin Turner, Mainsail Incentive Program, LLC 09/23/2021 Signature of Reporting Person Date /s/ Gavin Turner, Mainsail Management Company, LLC 09/23/2021 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Consists of (i) 31,672,405 shares Class B common stock (and associated common units in Brilliant Earth LLC ("LLC Units")) held by Mainsail Partners III, L.P. ("MP III"), (ii) 62,963 shares of Class B common stock (and associate LLC Units) held by Mainsail Incentive Program, LLC ("MIP"), and (iii) 700,227 shares of Class B common stock (and associated LLC Units) held by Mainsail Co-Investors III, L.P. ("MCOI"). Shares of Class B common stock of the Issuer confer no economic rights on the holders thereof. Holders of shares of Class B common stock will be entitled to one vote per share on all matters to be voted on by holders of the Issuer's shares of Class A common stock. Upon exchange of LLC Units that are held by the reporting persons and reported in Table II hereof, an equal number of shares of Class B common stock will be delivered to the Issuer and cancelled for no consideration. LLC Units do not expire. ( 2 )Mainsail GP III, LLC ("GP III") is the general partner of MP III. MCOI is a co-investment vehicle that invests alongside MP III. GP III is the general partner of MCOI. A three member investment committee of GP III acts by a majority vote with Gavin Turner possessing a veto right with respect to the voting and dispositive power of the securities held by MP III and MCOI. Mainsail Management Company, LLC ("MMC") is the managing member of MIP and Gavin Turner is sole Manager of MMC. Mr. Turner has separately reported the securities held by each of the foregoing on his Form 3 filed in his capacity as a director of the Issuer. The reporting persons disclaim beneficial ownership of the reported securities except to the extent of their respective pecuniary interests therein.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

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