TOURMALINE? FERBERITE? OTHER?

[605dano]

Picked these rocks up the other day and thought was tourmaline. But I can scratch with my knife. Streak was a charcoal grey. Don't add up, Ferberite maybe? I don't know, any ideas?

 

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[BurntBear]

Looks like Ferberite. Can you do a specific gravity test? (Not the whole specimen; but a piece of the black part)

 

[DDancer]

Never seen that but the data matches your tests Neat.

 

[Eu_citzen]

Ferberite should have perfect cleavage and a black to brownish streak(?). I don't see any cleavage, so I kinda doubt it.

 

[605dano]

Eu I don't really understand about cleavage. My rock book says that ferberite has cleavage of [010] Perfect,[100]Parting,[102]Parting. What does that mean?

 

[Eu_citzen]

Right, cleavage is basically a structural weakness in the atomic structure of the mineral. So it "Cleaves" repeatable the same way. Often leaving flat surfaces.
Google for pictures of "cleavage+minerals".... Do add "minerals" or you'll end up wrong.

Parting is a different, complicated ball game. It looks like cleavage but isn't repeatable the same way.

 

[Bajahunter]

I once saw a National Geographic that had pictures of the cleavage of amazonites.