"I started out making teapots 40 years ago, and here I am still making teapots. They used to work but now they're just paper weights. They're becoming more and more abstract.
"This exhibition isn't really about rocks - they're actually pieces of clay that I've dried out and smashed up. They come out as rock forms which I fit together."
Mr Lange said the results can sometimes surprise him.
"I'm looking for the bright, strong colours and contrasts, and a certain liveliness to them."
He said making the wacky, abstract teapots were "the most fun I've had".
"The lid doesn't have to fit, the spout doesn't have to pour, the handle doesn't have to be practical. It's just the essence of a teapot."
Among the many ceramic forms Mr Lange has tried, one of his most well-known is brickwork. He has made many remarkable shapes out of bricks, including boats, punctuation marks, seats, caravans and vegetables.
However, he is in the middle of shutting down his brickwork operation.
"You might say it's part of the retirement process," he said.
Mr Lange's work is complemented by paintings by local artist Mike Marsh.
Rock Dreams runs until July 23.