Cosmic necklaces are hybrid topological defects consisting of monopoles and strings .
We argue that primordial black holes ( PBHs ) may have formed from loops of the necklaces , if there exist stable winding states , such as coils and cycloops .
Unlike the standard scenario of PBH formation from string loops , in which the kinetic energy plays important role when strings collapse into black holes , the PBH formation may occur in our scenario after necklaces have dissipated their kinetic energy .
Then , the significant difference appears in the production ratio .
In the standard scenario , the production ratio f becomes a tiny fraction f \sim 10 ^ { -20 } , however it becomes f \sim 1 in our case .
On the other hand , the typical mass of the PBHs is much smaller than the standard scenario , if they are produced in the same epoch .
As the two mechanisms may work at the same time , the necklaces may have more than one channel of the gravitational collapse .
Although the result obtained in this paper depends on the evolution of the dimensionless parameter r , the existence of the winding state could be a serious problem in some cases .
Since the existence of the winding state in brane models is due to the existence of a non-tivial circle in the compactified space , the PBH formation can be used to probe the structure of the compactified space .
Black holes produced by this mechanism may have peculiar properties .