A record 1200 people, including about 30% men, packed the Crown Perth ballroom today.
Farrell, who is Rio group executive, health, safety and environment and managing director of the Australian operations, finished full-time work today.
When Farrell started her career in 1979, there was no discussion around gender equality and most workplaces had "girly" magazines and calendars on display.
"One of the great gender equality achievements at that time was to get them down," she said.
"How far we have come."
While the focus is how much there is to do still, Farrell assured the crowd the cause of women in mining had come a long way during her career.
"We should not forget to celebrate what has been achieved," she said.
Still the latest statistics on gender diversity in the ASX 200 are alarming.
Only 6% of CEOs across all sectors are women and only 25% of total executives are women.
Farrell noted the number of women in line roles had shown the least improvement at only 13%, which highlighted the importance of attracting women to study STEM subjects.
She advised women in the industry to be curious, see the world through opportunity, not challenge, and to not be a bystander.
"Be sure what you stand for," she said.
Farrell said the report into sexual harassment due to be handed down by Sex Discrimination Commissioner Kate Jenkins would likely be "confronting and require us all to take action".
"None of this can be left as a women's issue," she said.
"It's about men and women standing side-by-side."
Farrell worked under former Rio CEO and then head of the iron ore business Sam Walsh when she was named Women in Resources Champion by the Chamber of Minerals and Energy of WA in 2012.
"He said to me ‘I never see you as a woman'. Please don't take offence to that - I didn't," she said.
"To him, I was a member of his team … someone who got things done."
Farrell stressed that improving gender diversity was not about fixing women, but breaking down barriers.
"I urge you to demand that [society] changes traditional gender views," she said.
"There's still a lot to do - we should be impatient about it."
Earlier at the event, ABC journalist Leigh Sales interviewed South32 CEO and chairman of CEOs for Gender Equity Graham Kerr.
She opened with a question usually reserved for females by asking how he juggled his role as CEO with family life.
Kerr said he tried to encourage flexible working hours by taking them himself, like taking a Friday afternoon off to spend with his four children after an overseas trip.
He said there had been some resistance from areas of the workforce regarding gender diversity.
"Certainly some of the pushback from typical white Anglo males has been interesting," Kerr said.
The main concerns among them were that a push to hire women might hurt their chances of promotion, or prevent their sons from getting jobs in the future.
Kerr said it was important to talk about the reasons for gender diversity.
He said all sorts of diversity were important for a vibrant and innovative workforce.
Two of Kerr's four children are girls and he wants them to have the same opportunities in life as his sons.
"The last one is pure business sense - we're not accessing half the talent pool," he said.
South32 has a female chair and CFO and the top 60 employees were about 37% women.
Overall, the company has just 18% females in its workforce, similar to other major mining companies.
Kerr called on male leaders in the mining sector to do more.
"Today the deck is unevenly stacked and they're in positions of power. If they can't change it, who can?"