The first two diamond core holes intersected 69m (40m estimated true width) grading 6.52g/t gold in EMD18-053; and 44.7m (17m est. true width) at 2.82g/t in EMD18-052, both from surface.
"Hole EMD18-053 is the company's best drill hole to date on the project," president Yannis Tsitos said.
He said these first deeper holes at Salbora, 1.5km from Eagle Mountain, increased understanding of previously announced high-grade results.
The holes were drilled below a surface trench which had returned 123m at 1.92g/t gold in May 2018.
The company is drilling to increase the saprolite resource at the project where it is aiming for larger-scale production in 2020, having run a gravity pilot plant in 2016-2017.
It is planning a 10-15 hole step-out diamond core drilling programme in the first half of this year.
The project's existing saprolite resource comprises an indicated 1.59 million tonnes at 1.45g/t gold for 74,100 ounces and an inferred 7.2Mt at 1.32g/t for 305,600oz.
IAMGOLD holds 4% of Goldsource.
The company completed an upsized C$1.3 million (US$0.97 million) raising last week at 5c per unit, towards Eagle Mountain resource expansion, pre-feasibility study costs and general corporate purposes.
Goldsource shares, which had lingered around 5c in December, soared yesterday to 14c intraday, a level last seen in the first half of 2017.
They closed up more than 73% or 5c to 13c, capitalising it close to $29 million.