How to sort unknown ferrite cores

1 turnDo a single loop through the core windows and measure the impedance with some sort of analyzer. Even an MFJ259B with a short connection to the jack will work well for this. If X=R someplace much higher, you can be sure it is a different mix. The Q=1 frequency, where X=R or where loss tangent crosses reactance, tells you the material better than anything else you can do.

Ferrite materials