Mountain Province Diamonds Announces Updated Mineral Resource Estimate for Gahcho Kué Diamond Project

    Shares Issued and Outstanding: 59,932,381
    TSX: MPV
    AMEX:   MDM

               Indicated Mineral Resource 50.5 Million Carats
                Inferred Mineral Resource 10.3 Million Carats

    TORONTO and NEW YORK, May 26 /CNW/ - Mountain Province Diamonds Inc.
(TSX: MPV, AMEX:   MDM) (the "Company") today announced the results of an
updated mineral resource estimate for the Gahcho Kué diamond project located
in Canada's Northwest Territories.
    The updated National Instrument (NI) 43-101 resource report, summarized
in Table 1 below, was prepared by AMEC Americas Limited (AMEC). This report
describes an updated mineral resource estimate on the Gahcho Kué diamond
project that incorporates information from geological and diamond revenue data
updates completed since the previous Technical Report in 2003.

    Table 1: Gahcho Kué 2009 Mineral Resource Summary
    (Effective Date April 20, 2009)

    Pipe           Resource         Volume      Tonnes     Carats      Grade
                Classification       (Mm3)       (Mt)       (Mct)      (cpht)
    5034          Indicated           5.1        12.7       23.9        188
                  Inferred            0.3         0.8        1.2        150
    Hearne        Indicated           2.3         5.3       11.9        223
                  Inferred            0.7         1.6        2.9        180
    Tuzo          Indicated           5.1        12.2       14.8        121
                  Inferred            1.5         3.5        6.2        175
    Summary       Indicated          12.4        30.2       50.5        167
                  Inferred            2.5         6.0       10.3        173

    1) Mineral Resources are reported at a bottom cut-off of 1.0 mm; cpht
       = carats per hundred tonnes.
    2) Mineral Resources are not Mineral Reserves and do not have
       demonstrated economic viability
    3) Volume, tonnes, and carats are rounded to the nearest 100,000
    4) Tuzo volumes and tonnes exclude 0.6 Mt of a granite raft
    5) Diamond price assumptions used to assess reasonable prospects of
       economic extraction reflect mid-2008 price books with a 20% increase
       factor. The prices assumed, on a per pipe basis (in US$), equate to
       $113/ct for 5034, $76/ct for Hearne and $70/ct for Tuzo.

    Commenting, Mountain Province President and CEO, Patrick Evans said:
"This updated mineral resource statement is the culmination of a fourteen-year
exploration and evaluation program and represents a major milestone in the
development of the Gahcho Kué project. In their report, AMEC confirms that the
scientific and technical data on the Gahcho Kué project is now of sufficient
quality and level of detail to support a feasibility study, which is currently
under consideration by the Joint Venture partners."
    Industry-standard techniques were used to ensure appropriate calculation
and reporting of the diamond resources at a +1 mm lower cut-off. The mineral
resources were adjusted for the expected main treatment plant response by
reducing recoveries in the lower size classes. AMEC had access to two sources
of diamond valuations - one from WWW International Diamond Consultants (WWW),
which is independent, and one from the Diamond Trading Company (DTC), which is
associated with the Gahcho Kué project operator, De Beers Canada Inc. ("De
Beers"). AMEC has relied on both valuations.
    To assess reasonable prospects for economic extraction to support
declaration of a mineral resource, diamond valuations from WWW and DTC were
analysed, and average mid-2008 pricing, with a 20 percent increase, was
applied to the resource blocks. It is common practice in the industry to
assume a higher long-term commodity price when determining a cut-off grade for
mineral resources than the long-term commodity price used for mineral reserves
or financial analysis. Average diamond pricing was only used to assess
reasonable prospects of economic extraction to support declaration of mineral
    All of the indicated mineral resources and a significant portion of the
inferred resources were shown to have reasonable prospects of economic
extraction through open-pit mining. The inferred resources of the Hearne pipe
material lying outside of the resource pit shell was, at least conceptually,
shown to have reasonable prospects of economic extraction using underground
mining methods. All the Gahcho Kué kimberlites remain open to depth.
    A copy of the full AMEC report will shortly be published on SEDAR and
EDGAR, and on the Company's website

    Mountain Province Diamonds (49 percent) is a joint venture partner with
De Beers Canada Inc. (51 percent) in the Gahcho Kué project. De Beers is the
operator of the project and can be called on to fund the project through to
commercial production. Located in Canada's Northwest Territories, Gahcho Kué
is one of the largest new diamond projects under development globally.

    Qualified Person

    The Qualified Person for the estimate is Ken Brisebois, P. Eng., an AMEC
employee. The estimation and classification of the mineral resources conform
to industry-best practices and meet the requirements of CIM (2005).

    Note to U.S. Investors

    This press release describes minerals which have been classified as
"indicated resources" and "inferred resources" under Canadian National
Instrument 43-101. We advise U.S. investors that while those terms are
recognized and required by Canadian regulations, the U.S. Securities and
Exchange Commission do not recognize them. "Inferred resources" have a great
amount of uncertainty as to their existence, and great uncertainty as to their
economic and legal feasibility. It cannot be assumed that all or any part of
an inferred mineral resource as defined under Canadian National Instrument
43-101 will ever be upgraded to a higher category. Under Canadian rules,
estimates of inferred mineral resources may not form the basis of feasibility
or pre-feasibility studies, except in rare cases. U.S. investors are cautioned
not to assume that any part or all of mineral deposits in these categories
will ever be converted into reserves nor that part or all of an inferred
resource exists, or is economically or legally minable.

    Forward-Looking Statements

    This news release may contain forward-looking statements, within the
meaning of the "safe-harbor" provision of the Private Securities Litigation
Reform Act of 1995, regarding the Company's business or financial condition.
Actual results could differ materially from those described in this news
release as a result of numerous factors, some of which are outside the control
of the Company.

    %CIK: 0001004530

For further information:

For further information: Mountain Province Diamonds Inc., Patrick Evans,
President and CEO, Tel: (416) 670-5114

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