[Osorio]

Puedes hacer algo como

Código Delphi [-]
procedure TForm1.Button1Click(Sender: TObject);
var
  f: TField;
  tipo: String;
begin
    case f.DataType of
      ftUnknown:  tipo:= 'ftUnknown';
      ftString:   tipo:= 'ftString';
      ftSmallint: tipo:= 'ftSmallint';
      ftInteger:  tipo:= 'ftInteger';
      ftWord:     tipo:= 'ftWord';
    end;
    {
    ftBoolean, ftFloat, ftCurrency, ftBCD, ftDate, ftTime, ftDateTime, // 5..11
    ftBytes, ftVarBytes, ftAutoInc, ftBlob, ftMemo, ftGraphic, ftFmtMemo, // 12..18
    ftParadoxOle, ftDBaseOle, ftTypedBinary, ftCursor, ftFixedChar, ftWideString, // 19..24
    ftLargeint, ftADT, ftArray, ftReference, ftDataSet, ftOraBlob, ftOraClob, // 25..31
    ftVariant, ftInterface, ftIDispatch, ftGuid, ftTimeStamp, ftFMTBcd, // 32..37
    ftFixedWideChar, ftWideMemo, ftOraTimeStamp, ftOraInterval, // 38..41
    ftLongWord, ftShortint, ftByte, ftExtended, ftConnection, ftParams, ftStream, //42..48
    ftTimeStampOffset, ftObject, ftSingle); //49..51
     }
end;