Police are investigating the high value theft from the site near Dumfries overnight from Monday to Tuesday.
The cable, which is four core armoured electrical cable, is the property of Tilhill Forestry.
Constable Dale McEwan said “We are seeking assistance from the public to help us in this inquiry.
“Anyone who may have been on the A701 road which runs past the quarry late on Monday evening or early on Tuesday morning is asked to call us on the 101 number if they saw or heard anything suspicious.
“We are particularly keen to hear about any suspicious vehicles movement over this time near the quarry entrance.”
Callers should quote the reference number 0743 29/10.