Posting this for Dean, who ha trouble with the upload.
Thrift store find. $10.00.
5 1/2" Long x 3 1/2" Wide.
26 oz or 760 grams.
I believe it to be volcanic, for two reasons. 1) Unpolished glass-like quality of the finish. 2) Heat holes.
I'm guessing that the white is Quartz, but that is just a guess.
This piece was a show piece before my purchase. I pulled some pieces of Silicone off of it, previously used in mounting.
If this is a piece you would like to show on your website, let me know and I will make sure you have some good digital prints.
That's about all I got. I'm fairly sure its just something cool, not necessarily high value, I've been playing around with rocks for 45 years, and I haven't seen this type before. I also couldn't find anything like it in a Bing Image search.