Christine MacRae - known as Renee - and her son Andrew were last seen driving out of Inverness on November 12, 1976.
Later that night, the 36-year-old mother-of-two’s BMW was found burned out in a lay-by on the A9 near Dalmagarry, 12 miles south of the city and the pair have not been seen since.
The investigation into their disappearance has been subject to ongoing reviews, which included a full cold case review in 2004, resulting in a month-long excavation of Dalmagarry Quarry.
Officers have started searching Leanach Quarry near Inverness with forensic teams “in order to establish any further opportunities to progress enquiries”.
Detective Inspector Brian Geddes said: “As part of the ongoing investigation into the disappearance of Renee and Andrew MacRae, officers are visiting key areas of interest in order to establish any further opportunities to progress enquiries.
“The passage of time is no barrier to the investigation of unresolved incidents of this nature.
“Police Scotland, along with our partners in the Scottish Police Authority Forensic Services, will continue to pursue any opportunities to progress the investigation, which will hopefully provide answers for the family of Renee and Andrew MacRae.
“Anyone with new information that could assist the investigation can call police on 101 or Crimestoppers on 0800 555 111.”