Is this a fossilized tree nut

[ashsap]

Okay, my boyfriend and I found this in Central Texas more specifically austin. At first we thought it was just some weird iron ball as it is heavy and feels just like metal. We were really confused and wanted to know more so we took a Dremel with a diamond cutting blade and tried to slice it open, it was extremely difficult to cut almost like we were cutting metal and we did not get very far maybe a quarter of an inch deep. I left it outside for a while for a couple months and we just kind of forgot about it until today we picked it up I asked him what he really thought it was and he said a piece of a metal decoration that somebody had outside and I was like nah but whatever and just dropped it onto my concrete steps at that point it hit at just the right way and cracked open into these pieces and as you can see the inside is obviously a nut of some sort it's hard as rock through and through the nut is just as hard as the outside and we instantly thought it was a petrified tree nut! Does anyone have any idea at all what this is?! Austin is known for having petrified wood and nuts of sorts so it could be. I don't know what are y'all's thoughts. Also the light green is just from the marker where we marked where we wanted to slice it.  Also as.you can see the outside is lumpy almost like a walnut but the inside is obviously not a walnut and walnuts outer shells are actually lumpy in a different way if that makes sense.  And it was perfectly round when together as one piece. 

Edited Tuesday at 12:51 AM by ashsap

[Harry Pristis]

Maybe iron pyrite . . . I've seen 'em marketed as "Boji Stones."

[val horn]

Not a seed or any kind of fossil.  Siderite/iron stone concretion  they form in layers like a snowball.  They can have fossils but often do not.