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

    <documentType>4</documentType><periodOfReport>2003-07-01</periodOfReport>
    <issuer>
        <issuerCik>0000891014</issuerCik>
        <issuerName>MINERALS TECHNOLOGIES INC</issuerName>
        <issuerTradingSymbol>MTX</issuerTradingSymbol></issuer><reportingOwner><reportingOwnerId>
            <rptOwnerCik>0001208981</rptOwnerCik>
            <rptOwnerName>BOURUET AUBERTOT ALAIN</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>0</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle>SENIOR VICE PRESIDENT</officerTitle></reportingOwnerRelationship></reportingOwner><derivativeSecurity><securityTitle><value>EMPLOYEE STOCK OPTION (RIGHT TO BUY)</value></securityTitle><conversionOrExercisePrice><value>49.12</value></conversionOrExercisePrice><transactionDate><value>2003-07-01</value></transactionDate><deemedExecutionDate><value>2003-07-01</value></deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>10000</value></transactionShares><transactionValue><value>0</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>1988-08-08</value><footnoteId id="F1"/></exerciseDate><expirationDate><value>1988-08-08</value><footnoteId id="F1"/></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>COMMON STOCK</value></underlyingSecurityTitle><underlyingSecurityShares><value>10000</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>20000</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeSecurity><derivativeSecurity><securityTitle><value>PHANTOM STOCK</value></securityTitle><conversionOrExercisePrice><value>49.12</value></conversionOrExercisePrice><transactionDate><value>2003-07-01</value></transactionDate><deemedExecutionDate><value>2003-07-01</value></deemedExecutionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>3900</value></transactionShares><transactionValue><value>0</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>3900</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>3900</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value></value></natureOfOwnership></ownershipNature></derivativeSecurity><footnotes><footnote id="F1">THE OPTION VESTS IN THREE EQUAL ANNUAL INSTALLMENTS BEGINNING ON JULY 1, 2004.</footnote><footnote id="F2">THE PHANTOM STOCK UNITS VEST IN TWO EQUAL INSTALLMENTS ON JULY 1, 2008 AND JULY 1, 2013.</footnote></footnotes><ownerSignature><signatureName>LINDA A. BUGGELN FOR ALAIN BOURUET-AUBERTOT</signatureName><signatureDate>2003-07-02</signatureDate></ownerSignature></ownershipDocument>

