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July 7 2008 - Mainstream Minerals Corporation (TSX.V: MJO) and King's Bay Gold Corporation (TSX.V: KBG) are pleased to announce that they have received additional drill results from Hole # 23 at their joint-ventured Bobjo Mine Project, located in Earngey and Agnew Townships, Red Lake, Ontario. This project continues to be the site of new discoveries that have so far included high-grade gold, rare earth elements and other minerals and metals.

The partners are pleased to report that numerous significant zones of rare earth elements and other minerals and metals were intersected in this Hole # 23 between 162.0 to 262.5 metres.

Results from this 100 metre wide mineralized zone included:

From 162.0 to 177.5 metres:

15.5 metres (50.1 ft) grading 34.57 g/t Sc (Scandium), 16.42 g/t Rb (Rubidium), 17.72 g/t Nd (Neodymium), 33.20 g/t Ce (Cerium), 33.46 g/t Li (Lithium), 8.46 g/t Cd (Cadmium), 6.26 g/t Sm (Samarium), 14.07 g/t Y (Yttrium), 15.53 g/t Ba (Barium), 45.67 g/t B (Boron), 4.83 g/t Hf (Hafnium), 5.14 g/t Yb (Ytterbium), 1.22 g/t Th (Thorium), 1.37 g/t Tb (Terbium), 12.35 g/t La (Lanthanum), 2.05 g/t Eu (Europium), 171.71 g/t Cr (Chromium), 160.84 g/t V (Vanadium), 157.30 g/t Sr (Strontium); and

0.0230 % Zn (Zinc), 0.188 % Ti (Titanium), 0.179 % P (Phosphorus), 0.196 % Mn (Manganese), 2.994 % Mg (Magnesium), 6.300 % Ca (Calcium), and 10.960 % Fe (Iron).

From 182.5 to 187.0 metres:

4.5 metres (14.8 ft) grading 19.40 g/t Sc (Scandium), 20.12 g/t Rb (Rubidium), 17.75 g/t Nd (Neodymium), 37.87 g/t Ce (Cerium), 9.10 g/t Li (Lithium), 5.56 g/t Sm (Samarium), 7.50 g/t Y (Yttrium), 25.71 g/t Ba (Barium), 17.40 g/t B (Boron), 5.50 g/t Hf (Hafnium), 4.00 g/t Yb (Ytterbium), 2.23 g/t Th (Thorium), 0.96 g/t Tb (Terbium), 16.38 g/t La (Lanthanum), 1.76 g/t Eu (Europium), 197.50 g/t Cr (Chromium), 52.21 g/t V (Vanadium), 49.00 g/t Sr (Strontium); and

0.0523 % Zn (Zinc), 0.0521 % Ti (Titanium), 0.121 % Mn (Manganese), 0.923 % Mg (Magnesium), 3.37 % Ca (Calcium), and 10.100 % Fe (Iron).

From 193.0 to 204.0 metres:

11.0 metres (36.1 ft) grading 29.10 g/t Sc (Scandium), 20.19 g/t Rb (Rubidium), 16.19 g/t Nd (Neodymium), 29.90 g/t Ce (Cerium), 11.91 g/t Li (Lithium), 5.85 g/t Sm (Samarium), 9.10 g/t Y (Yttrium), 46.39 g/t Ba (Barium), 25.00 g/t B (Boron), 4.42 g/t Hf (Hafnium), 4.61 g/t Yb (Ytterbium), 1.18 g/t Th (Thorium), 1.26 g/t Tb (Terbium), 11.66 g/t La (Lanthanum), 1.98 g/t Eu (Europium), 105.80 g/t Cr (Chromium), 88.34 g/t V (Vanadium), 73.78 g/t Sr (Strontium); and

0.0261 % Zn (Zinc), 0.100 % Ti (Titanium), 0.0517 % P (Phosphorus), 0.166 % Mn (Manganese), 1.361 % Mg (Magnesium), 5.090 % Ca (Calcium), and 11.911 % Fe (Iron).

From 208.25 to 262.50 metres:

54.25 metres (178.1 ft) grading 30.57 g/t Sc (Scandium), 5.01 g/t Rb (Rubidium), 15.31 g/t Nd (Neodymium), 26.23 g/t Ce (Cerium), 12.10 g/t Li (Lithium), 5.01 g/t Sm (Samarium), 11.01 g/t Y (Yttrium), 12.03 g/t Ba (Barium), 15.30 g/t B (Boron), 3.72 g/t Hf (Hafnium), 3.90 g/t Yb (Ytterbium), 1.00 g/t Th (Thorium), 1.23 g/t Tb (Terbium),10.51 g/t La (Lanthanum), 2.00 g/t Eu (Europium), 110.18 g/t Cr (Chromium), 109.00 g/t V (Vanadium), 55.11 g/t Sr (Strontium); and

0.0220 % Zn (Zinc), 0.0530 % P (Phosphorus), 0.101 % Ti (Titanium), 0.117 % Mn (Manganese), 1.101 % Mg (Magnesium), 5.210 % Ca (Calcium), and 13.270 % Fe (Iron).

All these minerals and metals have significant economic and strategic value. Some of these metals like Rubidium, which is not actively traded, has recently sold for as much as $100.00 US per gram. Recent selling prices for rare metals and rare earth elements can be seen at http://www.elementsales.com/

Rare Metals and Rare Earth Elements

Demand for rare metals and rare earth elements is soaring because of consumer demand for more fuel-efficient cars, alternative energy technologies such as fuel cells, the nuclear power industry for both practical and experimental utilization, rechargeable batteries, lasers, hydrogen storage, superalloys as used in the aerospace industry, televisions, computer screens, permanent magnets as used in electric-hybrid vehicles and in the conductor industry for many of the new "Green" technologies, etc. Currently, 97% of the world supply of the Rare Earth Materials (REM) comes from China. China recently announced a reduction in the exports of REMs coming out of their mines. This decision will considerably reduce the supply for buyers outside of China while world demand is in full growth.

The main consumers of rare earth materials are in South-East Asia (Japan, Korea, Thailand, and China) and in the USA. The United States used to be the largest consumer of rare earth materials, about 27% of the world's total. However, in recent years, China became the number one global consumer, exceeding the American consumption. The United States currently imports nearly 100% of their needs in REMs. It will soon become critical to produce these resources outside of China.

It is reported that 77% of world production is currently coming from one mine in China. The United States used to produce approximately 6% of the world's supply from one of the only in-situ rare earth mines in the world, at Mountain Pass, California. However, Mountain Pass — the only producing mine in North America — ceased operations several years ago, creating a situation where there is no Rare Earth Elements production taking place in North America, or anywhere significant outside of China. Therefore prices and demand are expected to continue to rise drastically.

Source: The data herein was collected from the United States Geological Survey (USGS) minerals information site.

This Bobjo Mine project is located between the former South Bay Zinc / Copper Mine and Uchi Lake Gold Mine. It is noted that an existing power line passes through the southern part of the property and that it is within trucking distance to the Placer Dome / Goldcorp Mill in Red Lake, Ontario. It is comprised of 259 claim units totaling 10,360 acres. The area has a history of gold and base metal production dating back 80 years. The work presently being carried out by the partners represents the commencement of the first modern, systematic exploration of the property in the last 80 years when a two compartment shaft was sunk to 270 feet with two levels in 1929.

The partners are very pleased with these new additional results. A 15,000 metre Phase 2 drilling program, as announced on March 3rd, 2008, is ongoing and additional results will be released when received and verified.

The joint venture is 50 % Mainstream Minerals (TSX.V: MJO) and 50 % Kings Bay Gold (TSX.V: KBG) with Mainstream Minerals being the Operator of the project. John Archibald, A.P.G.O. - Geologist is the Qualified Person under National Instrument 43-101. All of the samples herein were analyzed by Acurassay Labs. True widths are not known.

About Mainstream Minerals

Mainstream Minerals Corporation is a mineral exploration and development company focused on precious metal mining properties with economic potential, with the aim of bringing such properties to commercial production. The Company's portfolio of properties is primarily located in the prolific Red Lake Gold Camp of Northwestern Ontario. The properties include - (i) 50% of the Bobjo Mine project, (ii) 50 % of the Phyllis Lake project, (iii) 100% of the Dixie Lake North project, (iv) 50% of the Woman Lake North of South Bay project and (v) 100 % of the Stake Lake project.

MJO Shares Outstanding: 18,031,087

Mainstream Minerals CorporationNeil SullivanPresident & CEO(204)- 222-0137Email: [email protected]...

The TSX Venture Exchange has not reviewed and does not accept responsibility for the adequacy or accuracy of this release. Some of the statements contained in this release are forward-looking statements, such as estimates and statements that describe MJO's future plans, objectives or goals, including words to the effect that MJO's management expects a stated condition or result to occur. Since forward-looking statements address future events and conditions, by their very nature, they involve inherent risks and uncertainties.

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