![Smiley :)](http://www.glassmessages.com/Smileys/classic/smiley.gif)
It's not aventurine, it has been covered in silver foil, then blown a bit more, which breaks the foil up. It's just tarnished on the surface - rubbing it with your thumb should be enough to clean it up a bit.
![Grin ;D](http://www.glassmessages.com/Smileys/classic/grin.gif)
I do not understand why you'd have a mould seam of any description on a small round vase with a pontil scar. The scar comes from it being broken off the pontil rod after being blown; a mould blown piece won't have that, unless it was worked further after being taken out of the mould and this is not that complex.
I'm sorry, I don't have a clue who made it.
![Cry :'(](http://www.glassmessages.com/Smileys/classic/cry.gif)