Sierra Minerals Inc.
TSX : SIM

Sierra Minerals Inc.

August 21, 2007 13:07 ET

Sierra Intersects 68 Metres Grading 0.82 gm/t Gold at Cerro Colorado Mine, Mexico

Security Upgraded and Security Audit Commenced

TORONTO, ONTARIO--(Marketwire - Aug. 21, 2007) - Sierra Minerals Inc. ("Sierra") (TSX:SIM) is pleased to provide the results of its ongoing drill program at its 100% owned Cerro Colorado Gold Mine, in Sonora, Mexico. This is the first major drill program carried out by Sierra since acquiring the property in September 2006. To date the Company has completed 115-holes (6,565 metres) consisting of resource definition, exploration and ground sterilization drilling. This drilling is part of a planned, large, multi-phase drilling campaign for the Cerro Colorado Mine, which will be ongoing throughout 2007 and is intended to upgrade the historical mineral resource calculations to NI 43-101 compliance.

The mine produced approximately 14,000 ounces of gold in 2006 at a head grade of 0.76 gm/t. In the first six months of 2007 production at Cerro Colorado has increased and the mine produced a total 8,225 ounces at a head grade of 0.79 gm/t.

Of the total 115 holes drilled, 80 holes were drilled for resource calculation and exploratory reasons while the remaining 35 holes were drilled to sterilize potential waste rock areas for planned operations. Of the 80 resource and exploration holes, the 19 holes containing significant intercepts are reported in the table below. Highlights from the drill program at Cerro Colorado include drill hole GM-15 which intersected 68 meters of 0.82 gm/t gold and 2.66 gm/t silver at a depth of 52 metres below surface and drillhole GM-59 that intersected 26 meters at 1.18 gm/t gold from surface.

Martin Walter, Chief Executive Officer, commented: "As we have been increasing production at Cerro Colorado, we have also been drilling exploration holes to complete a NI 43-101 resource calculation. We expect to cut off drilling for this program by Q1 2008 for delivery of the calculation by Q2"



A summary of significant results is as follows:

--------------------------------------------------------------
HOLE EASTING NORTHING FROM TO WIDTH Gold Silver
No. (m) (m) (m) (m) (m) (g/t) (g/t)
--------------------------------------------------------------
GM 15 420301 3344098 52 120 68 0.82 2.66
--------------------------------------------------------------
Including 52 76 24 1.18 5.6
--------------------------------------------------------------
GM 18 420113 3343964 2 16 14 1.34 3.69
--------------------------------------------------------------
GM 19 420117 3343955 2 16 14 0.65 1.94
--------------------------------------------------------------
GM 21 420124 3343934 12 34 22 0.55 1.52
--------------------------------------------------------------
GM 22 420128 3343923 18 36 18 0.98 1.22
--------------------------------------------------------------
GM 27 420107 3343930 2 24 22 0.52 2.45
--------------------------------------------------------------
GM 28 420111 3343918 6 20 14 0.51 9.63
--------------------------------------------------------------
GM 29 420068 3343963 4 12 8 1.14 3.1
--------------------------------------------------------------
GM 31 420077 3343942 2 6 4 0.55 3.55
--------------------------------------------------------------
GM 32 420081 3343932 2 12 10 1.12 3.04
--------------------------------------------------------------
GM 34 420088 3343912 2 6 4 0.53 0.85
--------------------------------------------------------------
GM 35 420114 3343907 2 12 10 0.61 1.22
--------------------------------------------------------------
20 22 2 2.36 0.1
--------------------------------------------------------------
GM 59 420264 3343868 0 26 26 1.18
--------------------------------------------------------------
Including 0 8 8 2.68
--------------------------------------------------------------
GM 61 420197 3343866 30 32 2 8.8
--------------------------------------------------------------
50 52 2 15.15
--------------------------------------------------------------
GM 92 420318 3344307 30 44 14 1.07 2
--------------------------------------------------------------
GM 94 420315 3344244 4 16 12 0.59 1.83
--------------------------------------------------------------
74 78 4 2.04 3.5
--------------------------------------------------------------
76 80 4 0.59 4.9
--------------------------------------------------------------
114 120 6 1.3 1
--------------------------------------------------------------
GM 107 420237 3344049 76 78 2 4.78 4
--------------------------------------------------------------
GM 108 420425 3343941 2 14 12 1.4 2.6
--------------------------------------------------------------
22 30 8 0.74 2.75
--------------------------------------------------------------
40 44 4 0.89 1
--------------------------------------------------------------
less
than
GM 110 420425 3343943 14 26 12 1.0 0.5
--------------------------------------------------------------
38 70 32 0.97 1
--------------------------------------------------------------

Note: The above intersections have been calculated with a 0.2 g/t mine
cut off grade. The majority of the drill holes were drilled at a dip of
60 degrees, which is roughly perpendicular to the dip of the known ore
systems. True widths are approximately 90 % of the reported widths. At
the Cerro Colorado mine site, Sierra has implemented a quality control
program to ensure best practices in chemical sampling and analysis of
surface and drill core samples. All assaying for the 19 holes reported
was completed by International Plasma Laboratories of Richmond BC Canada
and was independently checked by the company's on-site mine assay
laboratory. Under the guidelines of the NI 43-101, the required
qualified person for the Cerro Colorado Gold Mine is Mr. Stephen
Wetherup of CCIC, who is a professional geologist registered in British
Columbia, Canada.


Sierra has also introduced major new security measures at the mine. Armed security forces are currently at the mine and will remain in place, along with security vehicles, additional surveillance systems, construction of new barriers and implementation of new security procedures. Further, the Company has engaged the Canadian-based security firm of Wunderlich & Gladston to complete a full security audit on the mine and its infrastructure.

Sierra Minerals Inc. is a precious metals producing company focused on acquiring and developing advanced stage gold and silver deposits that have a likelihood of realizing near-term production. The Company's primary focus is Mexico although it is actively reviewing opportunities throughout the Americas. Sierra is committed to company-wide environmental and corporate social responsibility best practices.

This press release contains forward looking statements.

FORWARD-LOOKING STATEMENTS

This press release includes certain "forward-looking information" within the meaning of the Securities Act (Ontario), including, but not limited to, statements as to timing and extent of exploration programs, the availability of exploration results and the extent of future production from the Cerro Colorado Mine. As such, forward-looking information addresses future events and conditions and so involves inherent risks and uncertainties, as disclosed under the heading "Risk Factors" and elsewhere in Sierra documents filed from time to time with the Ontario Securities Commission and other regulatory authorities. Actual results could differ significantly from those currently projected as a result of, among those factors, adverse weather, regulatory changes, delays in receiving permits, accidents, delays in completing exploration activities and results of exploration activities, not all of which are in the control of Sierra. The forward-looking information contained herein is Sierra's reasonable estimate today of future events and conditions, but no assurance can be given that such events or conditions will occur.

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