A growing Omicron outbreak threatens to plunge Western Australia's lucrative mining sector into chaos amid renewed calls for the state to reopen its borders.

Twelve new local cases emerged on Monday, including seven linked to a Perth nightclub cluster. A further 42 infections were reported over the weekend.

About 80 workers at BHP's Yandi iron ore mine are isolating after being identified as contacts of a rail contractor who tested positive while on site.

The contractor had returned a negative rapid antigen test last week before flying to the site in the state's north.

They felt unwell on Sunday and subsequently returned a positive PCR test.

BHP late on Monday confirmed one of the worker's colleagues had also tested positive. They have not reported any symptoms and have been in isolation.

"Contact tracing and deep cleaning at site is continuing, and other close and casual contacts remain in isolation as a precaution," a spokeswoman said.

"The health and wellbeing of our people is our top priority, and everyone impacted is being fully supported during their isolation period."

All contacts have returned negative rapid antigen tests but must return negative PCR tests before resuming work.

The infected workers face 14 days isolation at an accommodation camp under WA's strict laws, as does another contractor who tested positive at 29Metals' Golden Grove copper and zinc mine, about 450km northeast of Perth.

WA's Chamber of Minerals and Energy on Monday urged the government to immediately implement new close contact rules which would reduce quarantine periods to seven days and remove isolation for any casual contacts.

Premier Mark McGowan has maintained the proposed changes won't come into effect until WA has a higher caseload.

The premier has also declined to set a new border reopening date, having backflipped on a plan to resume travel from February 5.

He has cited the need to improve WA's booster rate, currently at 36 per cent, as a key reason for keeping the borders closed.

WA's chief health officer has advised the rate will reach 75 per cent by early March, at which point there would likely be waning immunity for more vulnerable people.

Opposition Leader Mia Davies called on the premier to reopen no later than March 5.

"The opposition supports vaccinations and public health measures, including mandates that are supported by health advice," she said.

"But you can't ignore the fact uncertainty is crippling businesses of all sizes ... the brain-drain of bright, innovative, talented people we need for WA to thrive post-COVID has already started and our reputation as a solid and stable state has been damaged."

Proof of double-dose vaccination is now required at virtually all public venues in WA, ranging from restaurants, cafes and pubs to gyms, play centres and even bottle shops.

The state-wide mandate, which came into effect overnight and prompted protests in the Perth CBD, applies to anyone aged 16 and above.

Customers who threaten or intimidate staff asking for proof of vaccination face up to 12 months' jail or a $50,000 fine.

Teachers and other education staff were also required to be double-dose vaccinated to work in schools as kids returned to classrooms on Monday.

Education Minister Sue Ellery said there would be teacher in front of every classroom in public schools, with about 90 staff yet to provide proof of vaccination.