Straight out of the psychedelic era(OK it missed by a year or two)...
I gave this to my mom in 1970 for her 40th birthday, at some point probably 20-25 years ago it was stuffed in one of her closets, not to light of day till a few days ago... I'd all but forgotten about it...
(http://i1358.photobucket.com/albums/q765/xxAMxx/misc/lava%20light%201970_zpsbrrfupta.jpg)
Far out!!!
I have a black one on my desk at home, lol. It's probably from the 80s though. I had a 70s one that looked just like yours but it got broken in my teens...