<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2021-06-24</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000007039</issuerCik>
        <issuerName>TRECORA RESOURCES</issuerName>
        <issuerTradingSymbol>TREC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001804502</rptOwnerCik>
            <rptOwnerName>Ortelius Advisors, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>450 PARK AVENUE, SUITE 2700</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10022</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001645708</rptOwnerCik>
            <rptOwnerName>Pangaea Ventures, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ORTELIUS ADVISORS, L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>450 PARK AVENUE, SUITE 2700</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10022</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001863646</rptOwnerCik>
            <rptOwnerName>Temnein Ventures III, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ORTELIUS ADVISORS, L.P.</rptOwnerStreet1>
            <rptOwnerStreet2>450 PARK AVENUE, SUITE 2700</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10022</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001804470</rptOwnerCik>
            <rptOwnerName>Desorcy Peter</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>450 PARK AVENUE, SUITE 2700</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10022</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2021-06-24</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>28076</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>8.18</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2551497</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnotes</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2021-06-25</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>58449</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>8.31</value>
                    <footnoteId id="F4"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2609946</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnotes</value>
                    <footnoteId id="F3"/>
                    <footnoteId id="F5"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The price reported in Column 4 is a weighted average price. The shares were purchased in multiple transactions at prices ranging from $8.08 to $8.30, inclusive. The reporting person undertakes to provide upon request to the issuer, the Securities and Exchange Commission or any security holder of the issuer full information regarding the number of shares purchased at each separate price within the range set forth in this footnote (1).</footnote>
        <footnote id="F2">These shares include 2,328,024 shares held by Pangaea Ventures, L.P. (&quot;Pangaea&quot;) and 223,473 shares held by Temnein Ventures III, L.P. (&quot;Temnein&quot;).</footnote>
        <footnote id="F3">Ortelius Advisors, L.P. (the &quot;Adviser&quot;) is the investment manager of Pangaea and Temnein. Peter DeSorcy is the sole member of the general partner of the Adviser, and Mr. DeSorcy has a controlling interest in the Adviser. The Adviser and Mr. DeSorcy disclaim beneficial ownership of any of the shares of common stock owned by Pangaea and Temnein, except to the extent of their pecuniary interest therein.</footnote>
        <footnote id="F4">The price reported in Column 4 is a weighted average price. The shares were purchased in multiple transactions at prices ranging from $8.25 to $8.35, inclusive. The reporting person undertakes to provide upon request to the issuer, the Securities and Exchange Commission or any security holder of the issuer full information regarding the number of shares purchased at each separate price within the range set forth in this footnote (4).</footnote>
        <footnote id="F5">These shares include 2,328,024 shares held by Pangaea and 281,922 shares held by Temnein.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>ORTELIUS ADVISORS, L.P. By: Ortelius Management, LLC, its general partner By: /s/ Peter DeSorcy Name: Peter DeSorcy Title: Managing Member</signatureName>
        <signatureDate>2021-06-28</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>PANGAEA VENTURES, L.P. By: Ortelius Advisors GP I, LLC, its general partner By: /s/ Peter DeSorcy  Name: Peter DeSorcy Title: Managing Member</signatureName>
        <signatureDate>2021-06-28</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>TEMNEIN VENTURES III, L.P. By: Temnein Advisors GP III, LLC, its general partner By: /s/ Peter DeSorcy Name: Peter DeSorcy Title: Managing Member</signatureName>
        <signatureDate>2021-06-28</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/  Peter DeSorcy</signatureName>
        <signatureDate>2021-06-28</signatureDate>
    </ownerSignature>
</ownershipDocument>
