The Toronto-based company said it had discovered the prospective TT8 deposit in an area previously mapped by the Ontario Geological Society and the deposit was believed to be hosted by an extension of a known greenstone belt to the east.
Harte said the 17 chip samples across a 40m strike length returned some of the highest surface-gold grades at Sugar Zone to date, ranging between 11.1-247 grams per tonne, in a vein 5-30cm wide.
Broader sampling of the hangingwall and footwall returned gold grades up to 2.64g/t, suggesting potential for a "significantly wider" mineralised zone, according to the company
Harte said the discovery would become the main focus of its exploration efforts as it tried to find additional feed for its mill.
"This exciting new discovery has all the attributes we have been looking for on the property. It is hosted in a Hemlo-style' sedimentary package of rocks and bears significant potential to form a part of a larger system," chief geologist David Stevenson said.
Follow-up diamond drilling is expected to start in January. Initial work is planned to test the down-dip potential. Based on assay results, drilling to test the strike extent would follow, the company said.
Harte is currently ramping up production at its Sugar Zone mine.
Harte recently adjusted its full-year guidance from 39,200oz to 24,000-26,000oz, at all-in sustaining costs of US$2,000-$2,200/oz, up from original guidance of $1,300-$1,350/oz.
The mine has been suffering from lower-than-expected underground development rates and the delayed start of a paste fill plant, as well as mine contractor issues.
The company is updating its mine plan and guidance for 2020.
The Sugar Zone mine has current indicated resources of 4.24 million tonnes grading 5.88g/t gold for 1.1Moz.
Harte's share price (TSX:HRT) has gained more than 80% in the past five trading days, but closed 8% lower on Monday at C17.5c to take the 12-month loss to 51%. The company's shares have been trading in a range between 9-44c over the past 12 months. It has a market capitalisation of $118 million.