Glasgow University Archaeological Research Division (Guard) believes it may have been dropped by a primitive hunter, or it could simply have been lost by a local antiquarian.
Researchers are considering the possibility that it may have arrived from another part of the country and then been lost by a local collector or a teacher at the former parish school in Durness.
The 3cm relic was made from a rock called black chert.
In a report by Guard made available on Highland Council's Highland Historic Environment Record, archaeologists said if the find was from Durness it had "cast an unexpected light" on the area's prehistoric times.
Guard's investigations at the schoolhouse at Loch Croispol is part of community company Durness Development Group's wider efforts to interpret the area's past.
Durness Parish School fell into a ruined state after its last master was sacked in 1861.
Built in the 1760s, following a campaign by local minister the Reverend Murdo MacDonald, the school had a classroom and accommodation for its teacher.