<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0101</schemaVersion>

    <documentType>4</documentType><periodOfReport>2003-05-22</periodOfReport>
    <issuer>
        <issuerCik>0000891014</issuerCik>
        <issuerName>MINERALS TECHNOLOGIES INC</issuerName>
        <issuerTradingSymbol>mtx</issuerTradingSymbol></issuer><reportingOwner><reportingOwnerId>
            <rptOwnerCik>0001033874</rptOwnerCik>
            <rptOwnerName>PASQUALE MICHAEL F</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>1</isDirector><isOfficer>0</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther></reportingOwnerRelationship></reportingOwner><derivativeSecurity><securityTitle><value>Phantom Stock Units</value></securityTitle><conversionOrExercisePrice><value>0</value><footnoteId id="F1"/></conversionOrExercisePrice><transactionDate><value>2003-05-22</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>500</value></transactionShares><transactionValue><value>45.55</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>1988-08-08</value><footnoteId id="F2"/></exerciseDate><expirationDate><value>1988-08-08</value><footnoteId id="F2"/></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>500</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>4162.478</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeSecurity><footnotes><footnote id="F1">Each Phantom Stock Unit, when redeemed, will have the value of one share of the Company's common stock on the first business day of the month in which payment is made.</footnote><footnote id="F2">The Phantom Stock Units were accrued under the Minerals Technologies Inc. Non-Funded Deferred Compensation and Unit Award Plan for Non-Employee Director's and are to be settled in cash upon the reporting person's retirement, the date of which is unknown at this time.</footnote></footnotes><ownerSignature><signatureName>S. Garrett Gray for Michael F. Pasquale </signatureName><signatureDate>2003-05-23</signatureDate></ownerSignature></ownershipDocument>

