A nine-day processing run through FMR's nearby Greenfields mill is said to have generated 840 ounces of unrefined gold, worth about A$2.1 million at current spot prices.
The production estimate is still to be reconciled with gold-in-circuit and refining adjustments.
The dore has been shipped to the Perth Mint for refining and sale.
Revenue, which is expected in the coming weeks, will be split evenly between the partners.
The run involved processing 20,500 tonnes of low-grade development ore from the underground drives within the mine, within the Burbanks mining centre, Western Australia, with the grade in line with the resource model.
Underground stoping of high-grade areas is underway, and is expected to generate some 60,000-75,000t of ore to support up to three additional processing campaigns over the next six months.
The pair announced the trial mining program more than a year ago.
FMR, which is a major Greenstone shareholder, is carrying all the mining and financing risks within the stage one area, targeting the Main Lode, beneath the Christmas pit, to a maximum 75m.
The data is expected to generate a better understanding of the orebody, and ultimately unlock the wider 145,700oz Burbanks gold project.
While the area has historically produced 421,000oz grading 10.9 grams per tonne, mining was largely limited to 140m depth.
The mineralisation remains open at depth with no exploration below 350m.
Greenstone hopes Burbanks is potentially analogous to other high-grade WA mines including Bellevue, Jundee, Darlot, Agnew and Gwalia which extend from 800-1600m below surface.
Managing director Chris Hansen said the 12-month trial would provide invaluable technical information associated with the geology, mining, and processing.
It should also help generate cash to fund Greenstone's plans to aggressively build resources along the 4km-long Burbanks trend, which also contains the Birthday Gift mine and largely untested areas to the north and south.
Late last year the company had drilling success, with high-grade hits at Burbanks North, where the mineralisation was previously thought to terminate due to faulting.
Further assays are pending, and new drilling is about to commence later this month.
Greenstone shares have traded between 1.8c and 3.1c over the past year, and opened down 3% this morning at 2.8c, valuing it at $23 million.