A six-year-old from Kent was over the moon to discover a 100-million-year-old fossil when searching for stones to skim at the beach.

Henry Dibb-Fuller from Ash, near Sandwich, was at St Margaret’s Bay last month with his mum and dad when he stumbled on the rare find.

His mum, Sam Dibb-Fuller, said she was amazed to later find out that the ‘stone’ was much more valuable than they initially thought, adding it was like “finding a gold bar”.

“We’d gone down the beach because we were a bit bored and me being a photographer, the beach when it’s windy is quite atmospheric for pictures,” she said.

“We went to St Margaret’s Bay. My husband and Henry were throwing stones into the sea and I was at the top of the beach. All of a sudden Henry came running up to me with the fossil.

“He said ‘Mummy, look what I’ve found’. He’s always bringing stones and things to me but this one was rather unusual.

“I said to him I thought it was really different and didn’t know what it was. He asked to take it home and usually, I say to him we should leave stones at the beach but this one was so unusual that I thought we would try to find out what it was when we got home.”

“I know it’s not worth any money but it’s like finding a gold bar on the floor – it’s something you don’t expect...”

But, the 47-year-old says they all forgot about it until a few days later.

She said: “I just chucked it in my bag and kind of forgot about it!

“I got it out of my bag and said to my husband that I really didn’t know what it was because it looked so weird.

“I thought the stone was coated in something so I took some snaps of it and asked on Facebook if anyone knew what was coating this stone. I didn’t even think it was a fossil.”

A few people replied to Mrs Dibb-Fuller’s post including one man who told her it was a Micraster fossil which is more than 100 million years old.

“A little while later another guy posted and told me it was two fossils in one,” she added.

“He said its shell was riddled with Entobia cretacea which is a parasitic tunnelling sponge which gives it that weird brain-like appearance.

“It’s really unusual.”

Micraster is an extinct genus of echinoids (marine animals) from the late cretaceous to the early eocene period. Micraster was an infaunal echinoid living in a burrow below the sediment surface.

Meanwhile, Entobia cretacea is a trace fossil in a hard substrate formed by sponges as a branching network of galleries, often with regular enlargements termed chambers.

Henry was amazed at his find and said to his mum when he found out how old it was: “It's even older than you Mummy!”

Mrs Dibb-Fuller says her son loves the Natural History Museum in London and is fascinated by dinosaurs so is thrilled about it all.

She said: “I’m pretty sure we will be back fossil hunting. This was completely random but I think this has really sparked his interest now.”

The family still have the fossil and Mrs Dibb-Fuller says she might contact the Natural History Museum to see if it is of any interest to them.

“I know it’s not worth any money but it’s like finding a gold bar on the floor – it’s something you don’t expect,” she added.

“I’ve never in my life just randomly found a fossil so it’s a really unusual find.”