The worker was using a mine dozer to cut in a sump underground.
During the shift, the dozer was used for five hours to cut the hard stone floor.
The NSW Resources Regulator said the worker was wearing a dust monitor at the time.
"The worker was exposed to respirable quartz that exceeded the workplace exposure standard," it said.
The regulator said the risk of exposure to airborne contaminants must be considered during task planning.
"When it is identified that stone is going to be cut such as in sumps and overdrives, the hierarchy of controls should be followed," it said.
"Controls such as worker segregation, ventilation, sprays, scrubbers and curtains should be implemented before personal protective equipment is considered."
