Omai Gold files preliminary economic assessment on Omai Project, Guyana

(All dollar amounts are in United States dollars, unless otherwise stated)

Highlights of Omai Project Preliminary Economic Assessment

6.327 million ounces of gold ("Au") projected life-of-mine ("LOM") payable production over 18 years

$4.0 billion after-tax net present value at a 5% discount rate at base case $3,600/oz gold, increasing to $5.5 billion at $4,200/oz gold

24% after-tax internal rate of return at $3,600/oz gold, increasing to 30% at $4,200/oz gold

$1.427 billion initial capital and sustaining and growth capital of $928 million over LOM

4.1 year payback at $3,600/oz gold, decreasing to 3.4 years at $4,200/oz Au

$1,501/oz gold average cash operating costs and all-in sustaining costs ("AISC") 1 of $1,608/oz

$8.093 billion cumulative after-tax cash flows 2 over 18 years

351,488 oz Au per year projected average production over LOM, with peak year gold production reaching 435,667 ounces

1.35 g/t Au average head grade and 93% process recovery

5.9:1 average strip ratio for the open pit LOM

Toronto, Ontario--(Newsfile Corp. - August 19, 2026) - Omai Gold Mines Corp. (TSXV: OMG) (OTCQB: OMGGF) (" Omai Gold " or the " Company ") is pleased to announce positive results from its Preliminary Economic Assessment (the "PEA") for its 100%-owned Omai Property, in Guyana, South America. The PEA mine plan incorporates both the Wenot open pit deposit and the adjacent Gilt underground deposit. These support production averaging 351,488 ounces of gold per year over an 18-year mine life, with peak year production of 435,667 ounces. Total combined production from the two deposits is estimated at 6,326,775 ounces of payable gold. At a base case gold price of $3,600/oz, the project has an after-tax Net Present Value 5% ("NPV") of $4.0 billion, a 24% Internal Rate of Return ("IRR"), and a payback period of 4.1 years. At the recent spot price of $4,200/oz, the after-tax NPV 5% increa