Recognize this mineral? (Picture)

Factual Questions
1

I know it looks like something the cat brought up/excreted, but apparently it’s a chunk of rock my friend found. He’s wondering what it is, and I’m no help.

I submit his question, therefore, to the collective genius of the 'Dope. Anyone recognize it?

Thanks!

http://i587.photobucket.com/albums/ss320/cwthree/Mobile%20Uploads/FB_IMG_1429278151874.jpg

2

I should add that he found this in Arizona, but he didn’t say where in Arizona.

3

Chalcedony?

4

I’d agree with Beowulff, it looks a lot like chalcedony.

5

Thanks, **Beowulff **and swampspruce!