Another piece to identify. Got at flea market.

Question

Hi, this piece is one of the strangest minerals I’ve ever came in contact with. It looks like dog waste from the outside. From the inside it’s filled with hairy shaped pointing lines of an unknown mineral. It breaks very easy. It smells like pure metal. It’s not magnetic. Grey in color. Outside is brown. A lot of it has been fallen off so it’s a very messy rock to store somewhere. I get the smell of metal everywhere when I touch the rock and place it somewhere else. So I made the pictures inside the closet where I keep it to avoid those strange pieces falling everywhere leaving me with a metallic smell for days. Hope someone knows what it is. 

Answer 1

Could be some vegetation that calcified. Could be limestone. Put a drop of vinegar on some of the pieces that have broken up. If it fizzes up, it is probably limestone. The sample may even be solidified excrement from an ancient animal, if it were fossilized it would be called a copralite.