Magnetite cores?

[antimony]

Hi,  i am interested in making some magnetite cores for my coils,  and other stuff.  Firstly, becouse it is so nice that i can custom-make molds in various shapes and sizes, but also i heard that they do a pretty good job.
One guy compared it to Metglas, but im not sure thats right.

So,  what i wanted to ask was, have you any experience with this that you would like to share?

And the second question is about what i read in a swedish electronics forum, so i may have some trouble with translation,  but i hope you get it. 
Its about the mesh size of the powder, that the finer it is, the higher work frequency.
Do anyone know this?

Thanks in advance guys.

[Paul-R]

What are you trying to do with these cores?

[forest]

How to effectively crush ferrite core into ferrite dust ?

[antimony]

What are you trying to do with these cores?

Well,  i am in the process of making my first magnet pulse motor, and i have made two coils already,  both of them Bedini style cores, but im not satisfied with them becouse my rods are about 3 mm in diameter and i cant find any better here where i live.
Another project that i would like to try to replicate is the Thane Heins BITT, but also other transformer projects like Lawrence Tseungs magnetic frame, and others that dont come to mind right now. 

Also,  i forgot. Thanks for your reply.

[Jimboot]

I have a big chunk of it here. It does have a crystalline structure but I have never tried using it in cores.