The three-meter dinosaur is a life-like puppet which will enliven activities and add to the atmosphere for a series of science talks for adults and children including "Everything you ever wanted to know about dinosaurs", presented by Phil Hore from the National Dinosaur Museum.

Geoscience Australia's group leader for mineral systems Richard Blewett expected about 8000 people to walk through the grounds and get involved in displays.

"Visitors will be able to try panning for gold and semi-precious stones," he said. "We have big vats of sediment and we spike them with gold, sapphires, topaz and quartz.

"People can take home with them whatever they find. We will have our staff on hand to show you how to do it. People should come along and bring a sense of adventure. You get the rewards if you get the knack of it and we have people to show you how to get the knack."

Dr Blewett said the event aimed to show Australians the positive impact of geology and geoscience on their lives and advances in technology made by Australian scientists.

"We are doing tours of the tsunami warning centre and giving talks on using a super computer and satellite imagery to understand flood risk information and surveying Antarctica," he said.

"I don't think most people realise how geoscience affects them. The way we live in our modern world is greatly shaped by positioning and making sure our GPS system is the most accurate it can be.

"To have driver-less cars you need GPS which is accurate down to the centimetre. We are very proud of what we do and we want to showcase that to the community. We are world leaders in what we do here in geology and geoscience."

Dr Blewett said the talks would be streamed live on the Geoscience Australia website for those who could not attend the open day. The T.Rex will be making appearances at 11am, 12.30pm and 1.30pm. The open day will be from 10am to 3pm. The T.Rex appearing at the open day comes from Erth's Dinosaur Zoo .