Dia Met Minerals and BHP Diamonds Inc. Announce Ekati Diamond Mine Exploration Update.

KELOWNA, British Columbia--(BUSINESS WIRE)--Sept. 27, 1999--

BHP Diamonds Inc. (NYSE:BHP) and Dia Met Minerals Ltd. (TSE:DMM.A.) (AMEX:DMM.A) (TSE:DMM.B.) (AMEX:DMM.B) are pleased to provide the following update on recent exploration results for their diamond activities in the NWT.

The final results of exploration bulk samples from the 1999 winter program are as follows:

Pipe    Kimberlite        Kimberlite   Diamonds    Sample   Value
        Metres Drilled     Sampled     Recovered   Grade    (US$/
                          (tonnes)   greater than  Carats/  carat)
                                     1mm (carats)   Tonne

Gazelle    1052            240.7      141.38        0.59    $15.12
Phoenix     492            106.1      149.22        1.41    $24.78
Piranha     425             87.4      203.44        2.33    $29.72

The Gazelle and Piranha pipes are located in the Buffer Zone and the Phoenix pipe is located in the Core Zone. Commercial valuations of these samples were conducted in Antwerp in September by a number of diamond dealers, valuers and consultants, including BHP Diamonds Inc.'s sales office. The values do not include a 10% reduction of the average of the valuations received, as had been the previous practice for the joint venture, due to increased confidence and understanding of current market conditions enabled by recent sales of Ekati(TM) diamonds.

The Gazipe is estimated to be approximately 2 hectares in size. Phoenix, approximately 0.6 hectares, is a satellite pipe to the Point Lake kimberlite pipe. The Piranha pipe is estimated to be approximately 0.4 hectares and lies in Lac de Gras on the boundary between the Buffer Zone and property held by Diavik Diamond Mines Inc.

Microdiamond results were received for the spring exploration drilling program. All five of the kimberlite discoveries in the spring program are located in the Buffer zone. One of the five discoveries produced significant microdiamond results, and these data are summarised below. Drill hole 99-12 was a vertical hole and drill holes 99-09 and 99-10 were drilled with dips of 50 degrees and 45 degrees, respectively. The results listed were obtained from analysis of split NQ drill core samples submitted to an independent laboratory.

Pipe  Drill Hole  Interval  Interval Sample Number   Number  Total
Code   Number     From (m)   To (m)    kg    of       of      wt.
                                           stones    stones Carats
                                           less than greater
                                             0.5mm    than
                                                                 0.5mm

99-A   99-09        110.8    133.2   25.2    122       4     0.026
99-A   99-10         99.0    136.2   43.7     26      11     0.110
99-A   99-12         25.3    137.5  122.1    118      24     0.103

Overall, the three largest stones recovered from 99-A split core weighed 0.10, 0.04 and 0.03 carats, respectively.

The summer exploration drilling program was completed. Nine additional kimberlite pipes were discovered bringing the total number of confirmed kimberlite occurrences to 121. Five of the discoveries are within the buffer zone claims (36 known pipes to date) and four of the discoveries are within the core zone claims (85 known pipes to date). Microdiamond analyses are pending.

Dia Met is a publicly traded mineral exploration and development company with a primary focus on diamonds. The company owns a 29 per cent interest in the Core Zone joint venture of the Ekati(TM) Diamond Mine. BHP Diamonds Inc. is the operator of the mine which commenced production in October 1998.

James R. Rothwell, President, BHP Diamonds Inc.

Charles E. Fipke, Geologist and Director, Dia Met Minerals Ltd.

James E. Eccott, President Dia Met Minerals Ltd.

The American Stock Exchange and Toronto Stock Exchange have neither approved nor disapproved the information contained in this release.