A NSW goldmine forced to shut down for three months last year after an earthquake has again halted operations following a dam wall breach.

The wall of a tailings dam at the Cadia mine, about 20km south of Orange, partially collapsed on Friday after there were two magnitude 2.7 earthquakes in the region on Thursday.

Its operator Newcrest Mining said there was no threat to personal safety and it had secured the area around the dam.

A "comprehensive geotechnical monitoring system" was implemented, the company said on Saturday.

The material involved, which was contained within the southern dam, was described as "a slurry of finely ground rock, water and a low level of benign processing re-agents".

The mine was forced to shut down after it was hit by a magnitude 4.3 earthquake in April 2017 and didn't return to partial production until July, causing a huge hit to the company's first-half profit.