I do not think this is a real anything. I thought it was resin because it fluoresces under UV 395. I can see refractions of the light inside it that could be glass, could be quartz. I just performed a couple more tests and here is what happened.
 
I tried to set it on fire. No avail. It does smell a bit funky. I don't expect quartz to smell funky when I light it. I then scratched it along the bottom - not on the bit you can openly see - with a bit of known quartz and it did scratch. It does not smell like amber and it is clear in the wrong way. 
 
Pretty sure this is some kind of fakery but dunno what. Came in with an old crystal collection.
 
I will list this for next to nothing for someone to sell on. If it doesn't sell reasonably quickly then I will give it away for free. I also left myself a note in the diary to make a category on the website for stuff we think is fake, but that I still want to sell because I don't really want it. 
 
Fake doesn't mean ugly or unloveable.