What exactly is a Lava Lamp?

Mickey asks: What exactly is a Lava Lamp?
The original lava lamp was designed by the inventor of lava lamps and founder of the company “Mathmos”, Edward Craven Walker, revealed the invention of the Lava Lamp in 1963 and 1964 and has been in continuous British production since then. A classic lava lamp contains a standard incandescent lamp which heats a glass (traditionally tapered) vessel of a specific liquid and “lava”. The “lava” formula from a 1968 US patent consisted of water and a transparent or opaque mix of mineral oil, wax, and carbon tetrachloride. The clear water or mineral oil can is typically colored with bright shades of transparent dye. It is presumed that Walker came up with the idea for the lava lamp after watching a homemade egg timer as it was bubbling on a stovetop in a pub. He hired British inventor, David George Smith to develop his vision as well as the chemical formula, and the idea took off.