The well-connected junior reported a standout 0.32m interval of banded quartz vein displaying ginguro, silver sulphide minerals, assaying 118.5g/t gold and 1,410g/t silver, or 135.09g/t gold-equivalent.
Director and technical advisor Dr Quinton Hennigh said Omu Sinter, also known as Otoineppu Mine, was "clearly structurally linked" to the other high-grade gold-silver occurrences on the property.
The Newmont Goldcorp-backed company said it had recognised Omu Sinter as a prospective target in 2016 after noticing many homes in the area had rock gardens with large boulders of silica sinter, material formed by hot spring waters as they emerge from the ground and flow into shallow pools.
Rock chip sampling from the bluff where they were quarried had proved the sinter was strongly anomalous in gold, silver and pathfinder elements, Irving said.
The company appointed Canada's former ambassador to Japan, Mackenzie Clugston, as an advisor last month to provide independent and strategic counsel.
Newmont Goldcorp made a US$6 million strategic investment in Irving in April at C$2.16 per share in a non-brokered private placement.
Irving plans to spend US$5.4 million of the proceeds on exploration at the Omu gold project and $600,000 on an alliance between the two companies to identify exploration opportunities in Japan.
Irving shares rose almost 16% or C35c to an all-time high of $2.55 yesterday to capitalise it about $112 million.