Pyrite on what?

[Rickyrock]

Given this by someone who found it among a collection. I'm assuming it's pyrite crystals but I've never seen them in layered formations like this. What else is it?

 

[DDancer]

I see only pyrite The layering affect is most likely due to the ebb and flow of the mineral solution in the cavity where the crystals formed. Many minerals form in layering events in hydrothermal solutions as the fluid fills and empties from cavities in the rock. Layering events also occur as the same fluids increase/decrease in temperature as well as mineral contents of the solution. Its a nice piece.

 

[fransherrell]

Its shine and glow suggests that it is pyrite. It is this feature of it that has popularized it as fool's gold. It is very common and is found in sedimentary rocks. It commands lesser value because it is brittle and can be broken easily.